Golf balls having a foam center

ABSTRACT

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed composition selected from thermoset compositions and thermoplastic compositions. The core layers have different hardness and specific gravity levels. The specific gravity (density) of the foam inner core is preferably less than the density of the outer core layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/344,822, filed Nov. 7, 2016, which is a division of U.S. patentapplication Ser. No. 14/145,648, filed Dec. 31, 2013, now U.S. Pat. No.9,486,674, which is a continuation-in-part of U.S. patent applicationSer. No. 14/017,979, filed Sep. 4, 2013, now U.S. Pat. No. 9,327,166,which is a continuation-in-part of U.S. patent application Ser. No.13/872,354, filed Apr. 29, 2013, now U.S. Pat. No. 9,302,156, the entiredisclosures of which are hereby incorporated herein by reference.Application Ser. No. 14/145,648 is also a continuation-in-part of U.S.patent application Ser. No. 13/913,670, filed Jun. 10, 2013, now U.S.Pat. No. 9,126,083, the entire disclosure of which is herebyincorporated herein by reference. Application Ser. No. 14/145,648 isalso a continuation-in-part of U.S. patent application Ser. No.13/611,376, filed Sep. 12, 2012, now abandoned, the entire disclosure ofwhich is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to multi-piece golf balls havinga solid core formed from a foamed composition. Particularly, the corehas a foamed inner core (center) and at least one outer core layerformed from a thermoset or a thermoplastic composition.

BACKGROUND OF THE INVENTION

Both professional and amateur golfer use multi-piece, solid golf ballstoday. Basically, a two-piece solid golf ball includes a solid innercore protected by an outer cover. The inner core is made of a natural orsynthetic rubber such as polybutadiene, styrene butadiene, orpolyisoprene. The cover surrounds the inner core and may be made of avariety of materials including ethylene acid copolymer ionomers,polyamides, polyesters, polyurethanes, and polyureas.

In recent years, three-piece, four-piece, and even five-piece balls havebecome more popular. New manufacturing technologies, lower materialcosts, and desirable ball playing performance properties havecontributed to these multi-piece balls becoming more popular. Many golfballs used today have multi-layered cores comprising an inner core andat least one surrounding outer core layer. For example, the inner coremay be made of a relatively soft and resilient material, while the outercore may be made of a harder and more rigid material. The “dual-core”sub-assembly is encapsulated by a cover of at least one layer to providea final ball assembly. Different materials can be used to manufacturethe core and cover and impart desirable properties to the final ball.

In general, dual-cores comprising an inner core (or center) and asurrounding outer core layer are known in the industry. For example,Sugimoto, U.S. Pat. No. 6,390,935 discloses a three-piece golf ballcomprising a core having a center and outer shell and a cover disposedabout the core. The specific gravity of the outer shell is greater thanthe specific gravity of the center. The center has a JIS-C hardness (X)at the center point thereof and a JIS-C hardness (Y) at a surfacethereof satisfying the equation: (Y−X)≥8. The core structure (center andouter shell) has a JIS-C hardness (Z) at a surface of 80 or greater. Thecover has a Shore D hardness of less than 60.

Endo, U.S. Pat. No. 6,520,872 discloses a three-piece golf ballcomprising a center, an intermediate layer formed over the center, and acover formed over the intermediate layer. The center is preferably madeof high-cis polybutadiene rubber; and the intermediate and cover layersare preferably made of an ionomer resin such as an ethylene acidcopolymer.

Watanabe, U.S. Pat. No. 7,160,208 discloses a three-piece golf ballcomprising a rubber-based inner core; a rubber-based outer core layer;and a polyurethane elastomer-based cover. The inner core layer has aJIS-C hardness of 50 to 85; the outer core layer has a JIS-C hardness of70 to 90; and the cover has a Shore D hardness of 46 to 55. Also, theinner core has a specific gravity of more than 1.0, and the core outerlayer has a specific gravity equal to or greater than that of that ofthe inner core.

The core sub-structure located inside of the golf ball acts as an engineor spring for the ball. Thus, the composition and construction of thecore is a key factor in determining the resiliency and reboundingperformance of the ball. In general, the rebounding performance of theball is determined by calculating its initial velocity after beingstruck by the face of the golf club and its outgoing velocity aftermaking impact with a hard surface. More particularly, the “Coefficientof Restitution” or “COR” of a golf ball refers to the ratio of a ball'srebound velocity to its initial incoming velocity when the ball is firedout of an air cannon into a rigid vertical plate. The COR for a golfball is written as a decimal value between zero and one. A golf ball mayhave different COR values at different initial velocities. The UnitedStates Golf Association (USGA) sets limits on the initial velocity ofthe ball so one objective of golf ball manufacturers is to maximize CORunder such conditions. Balls with a higher rebound velocity have ahigher COR value. Such golf balls rebound faster, retain more totalenergy when struck with a club, and have longer flight distance asopposed to balls with low COR values. These properties are particularlyimportant for long distance shots. For example, balls having highresiliency and COR values tend to travel a far distance when struck by adriver club from a tee.

The durability, spin rate, and feel of the ball also are importantproperties. In general, the durability of the ball refers to theimpact-resistance of the ball. Balls having low durability appear wornand damaged even when such balls are used only for brief time periods.In some instances, the cover may be cracked or torn. The spin raterefers to the ball's rate of rotation after it is hit by a club. Ballshaving a relatively high spin rate are advantageous for short distanceshots made with irons and wedges. Professional and highly skilledamateur golfers can place a back spin more easily on such balls. Thishelps a player better control the ball and improves shot accuracy andplacement. By placing the right amount of spin on the ball, the playercan get the ball to stop precisely on the green or place a fade on theball during approach shots. On the other hand, recreational players whocannot intentionally control the spin of the ball when hitting it with aclub are less likely to use high spin balls. For such players, the ballcan spin sideways more easily and drift far-off the course, especiallyif it is hooked or sliced. Meanwhile, the “feel” of the ball generallyrefers to the sensation that a player experiences when striking the ballwith the club and it is a difficult property to quantify. Most playersprefer balls having a soft feel, because the player experience a morenatural and comfortable sensation when their club face makes contactwith these balls. Balls having a softer feel are particularly desirablewhen making short shots around the green, because the player senses morewith such balls. The feel of the ball primarily depends upon thehardness and compression of the ball.

Manufacturers of golf balls are constantly looking to differentmaterials for improving the playing performance properties of the ball.Different materials for constructing the core have been considered overthe years. For example, golf balls containing cores made from foamcompositions are generally known in the industry. Puckett and Cadorniga,U.S. Pat. Nos. 4,836,552 and 4,839,116 disclose one-piece, shortdistance golf balls made of a foam composition comprising athermoplastic polymer (ethylene acid copolymer ionomer such as Surlyn®)and filler material (microscopic glass bubbles). The density of thecomposition increases from the center to the surface of the ball. Thus,the ball has relatively dense outer skin and a cellular inner core.According to the '552 and '116 patents, by providing a short distancegolf ball, which will play approximately 50% of the distance of aconventional golf ball, the land requirements for a golf course can bereduced 67% to 50%.

Gentiluomo, U.S. Pat. No. 5,104,126 discloses a three-piece golf ball(FIG. 2) containing a high density center (3) made of steel, surroundedby an outer core (4) of low density resilient syntactic foamcomposition, and encapsulated by an ethylene acid copolymer ionomer(Surlyn®) cover (5). The '126 patent defines the syntactic foam as beinga low density composition consisting of granulated cork or hollowspheres of either phenolic, epoxy, ceramic or glass, dispersed within aresilient elastomer.

Aoyama, U.S. Pat. Nos. 5,688,192 and 5,823,889 disclose a golf ballcontaining a core, wherein the core comprising an inner and outerportion, and a cover made of a material such as balata rubber orethylene acid copolymer ionomer. The core is made by foaming, injectinga compressible material, gasses, blowing agents, or gas-containingmicrospheres into polybutadiene or other core material. According to the'889 patent, polyurethane compositions may be used. The compressiblematerial, for example, gas-containing compressible cells may bedispersed in a limited part of the core so that the portion containingthe compressible material has a specific gravity of greater than 1.00.Alternatively, the compressible material may be dispersed throughout theentire core. In one embodiment, the core comprises an inner and outerportion. In another embodiment, the core comprises inner and outerlayers.

Sullivan and Binette, U.S. Pat. No. 5,833,553 discloses a golf ballhaving core with a coefficient of restitution of at least 0.650 and acover with a thickness of at least 3.6 mm (0.142 inches) and a Shore Dhardness of at least 60. According to the '553 patent, the combinationof a soft core with a thick, hard cover results in a ball having betterdistance. The '553 patent discloses that the core may be formed from auniform composition or may be a dual or multi-layer core, and it may befoamed or unfoamed. Polybutadiene rubber, natural rubber, metallocenecatalyzed polyolefins, and polyurethanes are described as being suitablematerials for making the core.

Sullivan and Ladd, U.S. Pat. No. 6,688,991 discloses a golf ballcontaining a low specific gravity core and an optional intermediatelayer. This sub-assembly is encased within a high specific gravity coverwith Shore D hardness in the range of about 40 to about 80. The core ispreferably made from a highly neutralized thermoplastic polymer such asethylene acid copolymer which has been foamed. The cover preferably hashigh specific gravity fillers dispersed therein.

Nesbitt, U.S. Pat. No. 6,767,294 discloses a golf ball comprising: i) apressurized foamed inner center formed from a thermoset material, athermoplastic material, or combinations thereof, a blowing agent and across-linking agent and, ii) an outer core layer formed from a secondthermoset material, a thermoplastic material, or combinations thereof.Additionally, a barrier resin or film can be applied over the outer corelayer to reduce the diffusion of the internal gas and pressure from thenucleus (center and outer core layer). Preferred polymers for thebarrier layer have low permeability such as Saran® film (poly(vinylidene chloride), Barex® resin (acyrlonitrile-co-methyl acrylate),poly (vinyl alcohol), and PET film (polyethylene terephthalate). The'294 patent does not disclose core layers having different hardnessgradients.

Sullivan, Ladd, and Hebert, U.S. Pat. No. 7,708,654 discloses a golfball having a foamed intermediate layer. Referring to FIG. 1 in the '654patent, the golf ball includes a core (12), an intermediate layer (14)made of a highly neutralized polymer having a reduced specific gravity(less than 0.95), and a cover (16). According to the '654 patent, theintermediate layer can be an outer core, a mantle layer, or an innercover. The reduction in specific gravity of the intermediate layer iscaused by foaming the composition of the layer and this reduction can beas high as 30%. The '654 patent discloses that other foamed compositionssuch as foamed polyurethanes and polyureas may be used to form theintermediate layer.

Tutmark, U.S. Pat. No. 8,272,971 is directed to golf balls containing anelement that reduces the distance of the ball's flight path. In oneembodiment, the ball includes a core and cover. A cavity is formedbetween core and cover and this may be filled by a foamed polyurethane“middle layer” in order to dampen the ball's flight properties. The foamof the middle layer is relatively light in weight; and the core isrelatively heavy and dense. According to the '971 patent, when a golferstrikes the ball with a club, the foam in the middle layer actuates andcompresses, thereby absorbing much of the impact from the impact of theball.

Although some foam core constructions for gold balls have beenconsidered over the years, there are drawbacks with using such foammaterials. For example, one disadvantage with golf balls having a foamcore is the ball tends to have low resiliency. That is, the velocity ofthe ball tends to be low after being hit by a club and the ballgenerally travels short distances. Golf balls having foam inner coresare often referred to as reduced distance balls. There is a need for newballs having a foam core with improved resiliency that will allowplayers to generate higher initial ball speed. This will allow playersto make longer distance shots. The present invention provides new foamcore constructions having improved resiliency as well as otheradvantageous properties, features, and benefits. The invention alsoencompasses golf balls containing the improved core constructions.

SUMMARY OF THE INVENTION

The present invention is directed to a core assembly for a golf ballcomprising a foamed inner core layer and an outer core layer. The innercore layer has a diameter of from 0.100 inches to 1.100 inches. Theouter core layer has a thickness of from 0.100 inches to 0.750 inches.The specific gravity of the outer core layer is greater than thespecific gravity of the inner core layer.

In one embodiment, the inner core layer has a positive hardnessgradient, the outer core layer is formed from a thermoplasticcomposition and has a positive hardness gradient, and at least one ofthe inner core layer composition and the outer core layer composition isa highly neutralized polymer composition comprising an acid copolymer ofethylene and an α,β-unsaturated carboxylic acid, optionally including asoftening monomer selected from the group consisting of alkyl acrylatesand methacrylates; a non-acid polymer selected from the group consistingof polyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof; an organic acid or salt thereof; anda cation source present in an amount sufficient to neutralize greaterthan 80% of all acid groups present in the composition.

In another embodiment, the inner core layer has a positive hardnessgradient, the outer core layer is formed from a thermoplasticcomposition and has a zero or negative hardness gradient, and at leastone of the inner core layer composition and the outer core layercomposition is a highly neutralized polymer composition comprising anacid copolymer of ethylene and an α,β-unsaturated carboxylic acid,optionally including a softening monomer selected from the groupconsisting of alkyl acrylates and methacrylates; a non-acid polymerselected from the group consisting of polyolefins, polyamides,polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers,single-site catalyst polymerized polymers, ethylene propylene rubber,ethylene propylene diene rubber, styrenic block copolymer rubbers, alkylacrylate rubbers, and functionalized derivatives thereof; an organicacid or salt thereof; and a cation source present in an amountsufficient to neutralize greater than 80% of all acid groups present inthe composition.

In another embodiment, the inner core layer has a zero or negativehardness gradient, the outer core layer is formed from a thermoplasticcomposition and has a positive hardness gradient, and at least one ofthe inner core layer composition and the outer core layer composition isa highly neutralized polymer composition comprising an acid copolymer ofethylene and an α,β-unsaturated carboxylic acid, optionally including asoftening monomer selected from the group consisting of alkyl acrylatesand methacrylates; a non-acid polymer selected from the group consistingof polyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof; an organic acid or salt thereof; anda cation source present in an amount sufficient to neutralize greaterthan 80% of all acid groups present in the composition.

In another embodiment, the inner core layer has a zero or negativehardness gradient, the outer core layer is formed from a thermoplasticcomposition and has a zero or negative hardness gradient, and at leastone of the inner core layer composition and the outer core layercomposition is a highly neutralized polymer composition comprising anacid copolymer of ethylene and an α,β-unsaturated carboxylic acid,optionally including a softening monomer selected from the groupconsisting of alkyl acrylates and methacrylates; a non-acid polymerselected from the group consisting of polyolefins, polyamides,polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers,single-site catalyst polymerized polymers, ethylene propylene rubber,ethylene propylene diene rubber, styrenic block copolymer rubbers, alkylacrylate rubbers, and functionalized derivatives thereof; an organicacid or salt thereof; and a cation source present in an amountsufficient to neutralize greater than 80% of all acid groups present inthe composition.

In another embodiment, the inner core layer is formed from a foamedpolyurethane composition comprising mineral filler particulate in anamount of from 0.1 wt % to 9.0 wt %, based on the total weight of thefoamed polyurethane composition, and the outer core layer is formed froma non-foamed highly neutralized polymer composition comprising an acidcopolymer of ethylene and an α,β-unsaturated carboxylic acid, optionallyincluding a softening monomer selected from the group consisting ofalkyl acrylates and methacrylates; a non-acid polymer selected from thegroup consisting of polyolefins, polyamides, polyesters, polyethers,polyurethanes, metallocene-catalyzed polymers, single-site catalystpolymerized polymers, ethylene propylene rubber, ethylene propylenediene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers,and functionalized derivatives thereof; an organic acid or salt thereof;and a cation source present in an amount sufficient to neutralizegreater than 80% of all acid groups present in the composition.

In another embodiment, the outer core layer has a positive hardnessgradient and is formed from a thermoset composition, and the inner corelayer has a positive hardness gradient and is formed from a highlyneutralized polymer composition comprising an acid copolymer of ethyleneand an α,β-unsaturated carboxylic acid, optionally including a softeningmonomer selected from the group consisting of alkyl acrylates andmethacrylates; a non-acid polymer selected from the group consisting ofpolyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof; an organic acid or salt thereof; anda cation source present in an amount sufficient to neutralize greaterthan 80% of all acid groups present in the composition.

In another embodiment, the outer core layer has a zero or negativehardness gradient and is formed from a thermoset composition, and theinner core layer has a positive hardness gradient and is formed from ahighly neutralized polymer composition comprising an acid copolymer ofethylene and an α,β-unsaturated carboxylic acid, optionally including asoftening monomer selected from the group consisting of alkyl acrylatesand methacrylates; a non-acid polymer selected from the group consistingof polyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof; an organic acid or salt thereof; anda cation source present in an amount sufficient to neutralize greaterthan 80% of all acid groups present in the composition.

In another embodiment, the outer core layer has a positive hardnessgradient and is formed from a thermoset composition, and the inner corelayer has a zero or negative hardness gradient and is formed from ahighly neutralized polymer composition comprising an acid copolymer ofethylene and an α,β-unsaturated carboxylic acid, optionally including asoftening monomer selected from the group consisting of alkyl acrylatesand methacrylates; a non-acid polymer selected from the group consistingof polyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof; an organic acid or salt thereof; anda cation source present in an amount sufficient to neutralize greaterthan 80% of all acid groups present in the composition.

In another embodiment, the outer core layer has a zero or negativehardness gradient and is formed from a thermoset composition, and theinner core layer has a zero or negative hardness gradient and is formedfrom a highly neutralized polymer composition comprising an acidcopolymer of ethylene and an α,β-unsaturated carboxylic acid, optionallyincluding a softening monomer selected from the group consisting ofalkyl acrylates and methacrylates; a non-acid polymer selected from thegroup consisting of polyolefins, polyamides, polyesters, polyethers,polyurethanes, metallocene-catalyzed polymers, single-site catalystpolymerized polymers, ethylene propylene rubber, ethylene propylenediene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers,and functionalized derivatives thereof; an organic acid or salt thereof;and a cation source present in an amount sufficient to neutralizegreater than 80% of all acid groups present in the composition.

In the above embodiments, the highly neutralized composition comprisingan acid copolymer, a non-acid polymer, an organic acid or salt thereof,and a cation source optionally has one or more of the followingproperties:

-   -   (a) the acid copolymer does not include a softening monomer;    -   (b) the acid of the acid copolymer is selected from acrylic acid        and methacrylic acid;    -   (c) the acid of the acid copolymer is present in the acid        copolymer in an amount of from 15 mol % to 30 mol %, based on        the total weight of the acid copolymer;    -   (d) the non-acid polymer is an alkyl acrylate rubber selected        from ethylene-alkyl acrylates and ethylene-alkyl methacrylates;    -   (e) the non-acid polymer is present in an amount of greater than        50 wt %, based on the combined weight of the acid copolymer and        the non-acid polymer;    -   (f) the non-acid polymer is present in an amount of 20 wt % or        greater, based on the total weight of the highly neutralized        composition;    -   (g) the non-acid polymer is present in an amount of less than 50        wt %, based on the combined weight of the acid copolymer and the        non-acid polymer;    -   (h) the highly neutralized polymer composition has a solid        sphere compression of 40 or less and a coefficient of        restitution of 0.820 or greater;    -   (i) the highly neutralized polymer composition has a solid        sphere compression of 100 or greater and a coefficient of        restitution of 0.860 or greater;    -   (j) the organic acid salt is a metal salt of oleic acid;    -   (k) the organic salt is magnesium oleate;    -   (l) the organic salt is present in an amount of 30 parts or        greater, per 100 parts of acid copolymer and non-acid copolymer        combined; and    -   (m) the cation source is present in an amount sufficient to        neutralize 110% or greater of all acid groups present in the        composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a perspective view of a spherical inner core made of a foamedcomposition in accordance with the present invention;

FIG. 2 is a perspective view of one embodiment of upper and lower moldcavities used to make the dual-layered cores of the present invention;

FIG. 3 is a cross-sectional view of a three-piece golf ball having adual-layered core made in accordance with the present invention;

FIG. 4 is a cross-sectional view of a four-piece golf ball having adual-layered core made in accordance with the present invention;

FIG. 5 is a graph showing the hardness of a two (2) differentdual-layered core samples (each sample having a foam center andthermoset rubber outer layer) at different points in the respective corestructures per two examples of this invention;

FIG. 6A is a graph showing the hardness of a dual-layered core having adiameter of 0.5 inches (foam center and thermoplastic outer layer) atdifferent points in the core structure per an example of this invention;

FIG. 6B is a graph showing the hardness of a dual-layered core having adiameter of 0.5 inches (foam center and thermoplastic outer layer) atdifferent points in the core structure per an example of this invention;

FIG. 6C is a graph showing the hardness of a dual-layered core having adiameter of 0.5 inches (foam center and thermoplastic outer layer) atdifferent points in the core structure per an example of this invention;and

FIG. 6D is a graph showing the hardness of a dual-layered core having adiameter of 0.75 inches (foam center and thermoplastic outer layer) atdifferent points in the core structure per an example of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Golf Ball Constructions

Golf balls having various constructions may be made in accordance withthis invention. For example, golf balls having three piece, four-piece,and five-piece constructions with single or multi-layered covermaterials may be made. Representative illustrations of such golf ballconstructions are provided and discussed further below. The term,“layer” as used herein means generally any spherical portion of the golfball. More particularly, in one version, a three-piece golf ballcontaining a dual-layered core and single-layered cover is made. Thedual-core includes an inner core (center) and surrounding outer corelayer. In another version, a four-piece golf ball containing a dual-coreand dual-cover (inner cover and outer cover layers) is made. In yetanother construction, a four-piece or five-piece golf ball containing adual-core; casing layer(s); and cover layer(s) may be made. As usedherein, the term, “casing layer” means a layer of the ball disposedbetween the multi-layered core sub-assembly and cover. The casing layeralso may be referred to as a mantle or intermediate layer. The diameterand thickness of the different layers along with properties such ashardness and compression may vary depending upon the construction anddesired playing performance properties of the golf ball.

Inner Core Composition

In general, foam compositions are made by forming gas bubbles in apolymer mixture using a foaming (blowing) agent. As the bubbles form,the mixture expands and forms a foam composition that can be molded intoan end-use product having either an open or closed cellular structure.Flexible foams generally have an open cell structure, where the cellswalls are incomplete and contain small holes through which liquid andair can permeate. Such flexible foams are used for automobile seats,cushioning, mattresses, and the like. Rigid foams generally have aclosed cell structure, where the cell walls are continuous and complete,and are used for used for automobile panels and parts, buildinginsulation and the like.

In the present invention, the inner core (center) comprises alightweight foam thermoplastic or thermoset polymer composition that mayrange from relatively rigid foam to very flexible foam. Referring toFIG. 1, a foamed inner core (4) having a geometric center (6) and outerskin (8) may be prepared in accordance with this invention.

A wide variety of thermoplastic and thermoset materials may be used informing the foam composition of this invention including, for example,polyurethanes; polyureas; copolymers, blends and hybrids of polyurethaneand polyurea; olefin-based copolymer ionomer resins (for example,Surlyn® ionomer resins and DuPont HPF® 1000 and HPF® 2000, commerciallyavailable from DuPont; Iotek® ionomers, commercially available fromExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylicacid copolymers, commercially available from Dow Chemical Company; andClarix® ionomer resins, commercially available from A. Schulman Inc.);polyethylene, including, for example, low density polyethylene, linearlow density polyethylene, and high density polyethylene; polypropylene;rubber-toughened olefin polymers; acid copolymers, for example,poly(meth)acrylic acid, which do not become part of an ionomericcopolymer; plastomers; flexomers; styrene/butadiene/styrene blockcopolymers; styrene/ethylene-butylene/styrene block copolymers;dynamically vulcanized elastomers; copolymers of ethylene and vinylacetates; copolymers of ethylene and methyl acrylates; polyvinylchloride resins; polyamides, poly(amide-ester) elastomers, and graftcopolymers of ionomer and polyamide including, for example, Pebax®thermoplastic polyether block amides, commercially available from ArkemaInc; cross-linked trans-polyisoprene and blends thereof; polyester-basedthermoplastic elastomers, such as Hytrel®, commercially available fromDuPont or RiteFlex®, commercially available from Ticona EngineeringPolymers; polyurethane-based thermoplastic elastomers, such asElastollan®, commercially available from BASF; synthetic or naturalvulcanized rubber; and combinations thereof.

In a particular embodiment, the inner core layer is formed from a foamedHNP composition, wherein the HNP composition is formed by blending anacid polymer, a non-acid polymer, a cation source, and a fatty acid ormetal salt thereof. Such HNP compositions are disclosed further below assuitable compositions for forming the outer core layer.

Castable polyurethanes, polyureas, and hybrids ofpolyurethanes-polyureas are particularly desirable for forming the innercore layer because these materials can be used to make a golf ballhaving good playing performance properties as discussed further below.By the term, “hybrids of polyurethane and polyurea,” it is meant toinclude copolymers and blends thereof.

Basically, polyurethane compositions contain urethane linkages formed bythe reaction of a multi-functional isocyanate containing two or more NCOgroups with a polyol having two or more hydroxyl groups (OH—OH)sometimes in the presence of a catalyst and other additives. Generally,polyurethanes can be produced in a single-step reaction (one-shot) or ina two-step reaction via a prepolymer or quasi-prepolymer. In theone-shot method, all of the components are combined at once, that is,all of the raw ingredients are added to a reaction vessel, and thereaction is allowed to take place. In the prepolymer method, an excessof polyisocyanate is first reacted with some amount of a polyol to formthe prepolymer which contains reactive NCO groups. This prepolymer isthen reacted again with a chain extender or curing agent polyol to formthe final polyurethane. Polyurea compositions, which are distinct fromthe above-described polyurethanes, also can be formed. In general,polyurea compositions contain urea linkages formed by reacting anisocyanate group (—N═C═O) with an amine group (NH or NH₂). Polyureas canbe produced in similar fashion to polyurethanes by either a one shot orprepolymer method. In forming a polyurea polymer, the polyol would besubstituted with a suitable polyamine. Hybrid compositions containingurethane and urea linkages also may be produced. For example, whenpolyurethane prepolymer is reacted with amine-terminated curing agentsduring the chain-extending step, any excess isocyanate groups in theprepolymer will react with the amine groups in the curing agent. Theresulting polyurethane-urea composition contains urethane and urealinkages and may be referred to as a hybrid. In another example, ahybrid composition may be produced when a polyurea prepolymer is reactedwith a hydroxyl-terminated curing agent. A wide variety of isocyanates,polyols, polyamines, and curing agents can be used to form thepolyurethane and polyurea compositions as discussed further below.

To prepare the foamed polyurethane, polyurea, or other polymercomposition, a foaming agent is introduced into the polymer formulation.In general, there are two types of foaming agents: physical foamingagents and chemical foaming agents.

Physical Foaming Agents. These foaming agents typically are gasses thatare introduced under high pressure directly into the polymercomposition. Chlorofluorocarbons (CFCs) and partially halogenatedchlorofluorocarbons are effective, but these compounds are banned inmany countries because of their environmental side effects.Alternatively, aliphatic and cyclic hydrocarbon gasses such as isobuteneand pentane may be used. Inert gasses, such as carbon dioxide andnitrogen, also are suitable.

Chemical Foaming Agents. These foaming agents typically are in the formof powder, pellets, or liquids and they are added to the composition,where they decompose or react during heating and generate gaseousby-products (for example, nitrogen or carbon dioxide). The gas isdispersed and trapped throughout the composition and foams it.

Preferably, a chemical foaming agent is used to prepare the foamcompositions of this invention. Chemical blowing agents may beinorganic, such as ammonium carbonate and carbonates of alkalai metals,or may be organic, such as azo and diazo compounds, such asnitrogen-based azo compounds. Suitable azo compounds include, but arenot limited to, 2,2′-azobis(2-cyanobutane),2,2′-azobis(methylbutyronitrile), azodicarbonamide, p,p′-oxybis(benzenesulfonyl hydrazide), p-toluene sulfonyl semicarbazide, p-toluenesulfonyl hydrazide. Other foaming agents include any of the Celogens®sold by Crompton Chemical Corporation, and nitroso compounds,sulfonylhydrazides, azides of organic acids and their analogs,triazines, tri- and tetrazole derivatives, sulfonyl semicarbazides, ureaderivatives, guanidine derivatives, and esters such as alkoxyboroxines.Also, foaming agents that liberate gasses as a result of chemicalinteraction between components such as mixtures of acids and metals,mixtures of organic acids and inorganic carbonates, mixtures of nitrilesand ammonium salts, and the hydrolytic decomposition of urea may beused. Water is a preferred foaming agent. When added to the polyurethaneformulation, water will react with the isocyanate groups and formcarbamic acid intermediates. The carbamic acids readily decarboxylate toform an amine and carbon dioxide. The newly formed amine can thenfurther react with other isocyanate groups to form urea linkages and thecarbon dioxide forms the bubbles to produce the foam.

During the decomposition reaction of certain chemical foaming agents,more heat and energy is released than is needed for the reaction. Oncethe decomposition has started, it continues for a relatively long timeperiod. If these foaming agents are used, longer cooling periods aregenerally required. Hydrazide and azo-based compounds often are used asexothermic foaming agents. On the other hand, endothermic foaming agentsneed energy for decomposition. Thus, the release of the gasses quicklystops after the supply of heat to the composition has been terminated.If the composition is produced using these foaming agents, shortercooling periods are needed. Bicarbonate and citric acid-based foamingagents can be used as exothermic foaming agents.

Other suitable foaming agents include expandable gas-containingmicrospheres. Exemplary microspheres consist of an acrylonitrile polymershell encapsulating a volatile gas, such as isopentane gas. This gas iscontained within the sphere as a blowing agent. In their unexpandedstate, the diameter of these hollow spheres range from 10 to 17 μm andhave a true density of 1000 to 1300 kg/m³. When heated, the gas insidethe shell increases its pressure and the thermoplastic shell softens,resulting in a dramatic increase of the volume of the microspheres.Fully expanded, the volume of the microspheres will increase more than40 times (typical diameter values would be an increase from 10 to 40μm), resulting in a true density below 30 kg/m³ (0.25 lbs/gallon).Typical expansion temperatures range from 80-190° C. (176-374° F.). Suchexpandable microspheres are commercially available as Expancel® fromExpancel of Sweden or Akzo Nobel.

As an alternative to chemical and physical foaming agents or in additionto such foaming agents, as described above, other types of fillers thatlower the specific gravity of the composition can be used in accordancewith this invention. For example, polymeric, ceramic, and glass unfilledmicrospheres having a density of 0.1 to 1.0 g/cc and an average particlesize of 10 to 250 microns can be used to help lower specific gravity ofthe composition and achieve the desired density and physical properties.

Additionally, BASF polyurethane materials sold under the trade nameCellasto® and Elastocell®, microcellular polyurethanes, Elastopor® Hthat is a closed-cell polyurethane rigid foam, Elastoflex® W flexiblefoam systems, Elastoflex®E semiflexible foam systems, Elastofoam®flexible integrally-skinning systems, Elastolit®D/K/R integral rigidfoams, Elastopan®S, Elastollan® thermoplastic polyurethane elastomers(TPUs), and the like may be used in accordance with the presentinvention. Bayer also produces a variety of materials sold as Texin®TPUs, Baytec® and Vulkollan®elastomers, Baymer®rigid foams, Baydur®integral skinning foams, Bayfit®flexible foams available as castable,RIM grades, sprayable, and the like that may be used. Additional foammaterials that may be used herein include polyisocyanurate foams and avariety of “thermoplastic” foams, which may be cross-linked to varyingextents using free-radical (for example, peroxide) or radiationcross-linking (for example, UV, IR, Gamma, EB irradiation). Also, foamsmay be prepared from polybutadiene, polystyrene, polyolefin (includingmetallocene and other single site catalyzed polymers), ethylene vinylacetate (EVA), acrylate copolymers, such as EMA, EBA, Nucrel®-type acidco and terpolymers, ethylene propylene rubber (such as EPR, EPDM, andany ethylene copolymers), styrene-butadiene, and SEBS (any Kraton-type),PVC, PVDC, CPE (chlorinated polyethylene). Epoxy foams,urea-formaldehyde foams, latex foams and sponge, silicone foams,fluoropolymer foams and syntactic foams (hollow sphere filled) also maybe used.

In addition to the polymer and foaming agent, the foam composition alsomay include other ingredients such as, for example, cross-linkingagents, chain extenders, surfactants, dyes and pigments, coloringagents, fluorescent agents, adsorbents, stabilizers, softening agents,impact modifiers, antioxidants, antiozonants, and the like. Theformulations used to prepare the polyurethane foam compositions of thisinvention preferably contain a polyol, polyisocyanate, water, an amineor hydroxyl curing agent, surfactant, and a catalyst as describedfurther below.

In one preferred version, the foam composition includes nanoclayparticles, more preferably quaternary ammonium nanoclay particulate.While not wishing to be bound by any theory, it is believed that addingthe nanoclay to the foam composition helps improve the foam cellstructure and morphology. As the nanoclay is dispersed in the foamcomposition, it helps create a greater number of smaller sized foamcells. Thus, the foam cells are packed together more tightly and celldensity is increased. The dimensions and geometry of the foam cellsacross the matrix tends to be more uniform. The cell structure ismaintained as the nanoclay help prevent air from diffusing through thecell walls. The resulting foam material has greater compression strengthand modulus. Preferably, the foam composition contains about 0.25 toabout 2% and more preferably about 0.25 to about 0.75% of nanoclayparticles based on total weight of the composition. Since the additionof the nanoclay may have a catalytic effect on the reaction rate of thereactants used to make the polyurethane foam, it is preferred that thenanoclay be added during the curing step.

Properties of Polyurethane Foams

The polyurethane foam compositions of this invention have numerouschemical and physical properties making them suitable for coreassemblies in golf balls. For example, there are properties relating tothe reaction of the isocyanate and polyol components and blowing agent,particularly “cream time,” “gel time,” “rise time,” “tack-free time,”and “free-rise density.” In general, cream time refers to the timeperiod from the point of mixing the raw ingredients together to thepoint where the mixture turns cloudy in appearance or changes color andbegins to rise from its initial stable state. Normally, the cream timeof the foam compositions of this invention is within the range of about20 to about 240 seconds. In general, gel time refers to the time periodfrom the point of mixing the raw ingredients together to the point wherethe expanded foam starts polymerizing/gelling. Rise time generallyrefers to the time period from the point of mixing the raw ingredientstogether to the point where the reacted foam has reached its largestvolume or maximum height. The rise time of the foam compositions of thisinvention typically is in the range of about 60 to about 360 seconds.Tack-free time generally refers to the time it takes for the reactedfoam to lose its tackiness, and the foam compositions of this inventionnormally have a tack-free time of about 60 to about 3600 seconds.Free-rise density refers to the density of the resulting foam when it isallowed to rise unrestricted without a cover or top being placed on themold.

The density of the foam is an important property and is defines as theweight per unit volume (typically, g/cm³) and can be measured per ASTMD-1622. The hardness, stiffness, and load-bearing capacity of the foamare independent of the foam's density, although foams having a highdensity typically have high hardness and stiffness. Normally, foamshaving higher densities have higher compression strength. Surprisingly,the foam compositions used to produce the inner core of the golf ballsper this invention have a relatively low density; however, the foams arenot necessarily soft and flexible, rather, they may be relatively firm,rigid, or semi-rigid depending upon the desired golf ball properties.Tensile strength, tear-resistance, and elongation generally refer to thefoam's ability to resist breaking or tearing, and these properties canbe measured per ASTM D-1623. The durability of foams is important,because introducing fillers and other additives into the foamcomposition can increase the tendency of the foam to break or tearapart. In general, the tensile strength of the foam compositions of thisinvention is in the range of about 20 to about 1000 psi (parallel to thefoam rise) and about 50 to about 1000 psi (perpendicular to the foamrise) as measured per ASTM D-1623 at 23° C. and 50% relative humidity(RH). Meanwhile, the flex modulus of the foams of this invention isgenerally in the range of about 5 to about 45 kPa as measured per ASTMD-790, and the foams generally have a compressive modulus of 200 to50,000 psi.

In another test, compression strength is measured on an Instron machineaccording to ASTM D-1621. The foam is cut into blocks and thecompression strength is measured as the force required to compress theblock by 10%. In general, the compressive strength of the foamcompositions of this invention is in the range of about 100 to about1800 psi (parallel and perpendicular to the foam rise) as measured perASTM D-1621 at 23° C. and 50% relative humidity (RH). The test isconducted perpendicular to the rise of the foam or parallel to the riseof the foam. The Percentage (%) of Compression Set also can be used.This is a measure of the permanent deformation of a foam sample after ithas been compressed between two metal plates under controlled time andtemperature condition (standard—22 hours at 70° C. (158° F.)). The foamis compressed to a thickness given as a percentage of its originalthickness that remained “set.” Preferably, the Compression Set of thefoam is less than ten percent (10%), that is, the foam recovers to apoint of 90% or greater of its original thickness.

Methods of Preparing the Foam Composition

The foam compositions of this invention may be prepared using differentmethods. In one preferred embodiment, the method involves preparing acastable composition comprising a reactive mixture of a polyisocyanate,polyol, water, curing agent, surfactant, and catalyst. A motorized mixercan be used to mix the starting ingredients together and form a reactiveliquid mixture. Alternatively, the ingredients can be manually mixedtogether. An exothermic reaction occurs when the ingredients are mixedtogether and this continues as the reactive mixture is dispensed intothe mold cavities (otherwise referred to as half-molds or mold cups).The mold cavities may be referred to as first and second, or upper andlower, mold cavities. The mold cavities preferably are made of metalsuch as, for example, brass or silicon bronze.

Referring to FIG. 2, the mold cavities are generally indicated at (9)and (10). The lower and upper mold cavities (9, 10) are placed in lowerand upper mold frame plates (11, 12). The frame plates (11, 12) containguide pins and complementary alignment holes (not shown in drawing). Theguide pins are inserted into the alignment holes to secure the lowerplate (11) to the upper plate (12). The lower and upper mold cavities(9, 10) are mated together as the frame plates (11, 12) are fastened.When the lower and upper mold cavities (9, 10) are joined together, theydefine an interior spherical cavity that houses the spherical core. Theupper mold contains a vent or hole (14) to allow for the expanding foamto fill the cavities uniformly. A secondary overflow chamber (16), whichis located above the vent (14), can be used to adjust the amount of foamoverflow and thus adjust the density of the core structure being moldedin the cavities. As the lower and upper mold cavities (9, 10) are matedtogether and sufficient heat and pressure is applied, the foamedcomposition cures and solidifies to form a relatively rigid andlightweight spherical core. The resulting cores are cooled and thenremoved from the mold.

Hardness of the Inner Core

As shown in FIG. 1, a foamed inner core (4) having a geometric center(6) and outer skin (8) may be prepared per the molding method discussedabove. The outer skin (8) is generally a non-foamed region that formsthe outer surface of the core structure. The resulting inner corepreferably has a diameter within a range of about 0.100 to about 1.100inches. For example, the inner core may have a diameter within a rangeof about 0.250 to about 1.000 inches, or a diameter within a range ofabout 0.100 to about 0.500 inches, or a diameter within a range of about0.300 to about 0.800 inches, or a diameter within a range of about 0.400to about 0.800 inches. More particularly, the inner core preferably hasa diameter size with a lower limit of about 0.10 or 0.12 or 0.15 or 0.25or 0.30 or 0.35 or 0.40 or 0.45 or 0.50 or 0.55 inches and an upperlimit of about 0.50 or 0.55 or 0.60 or 0.65 or 0.70 or 0.80 or 0.90 or1.00 or 1.10 inches. The outer skin (8) of the inner core is relativelythin preferably having a thickness of less than about 0.020 inches andmore preferably less than 0.010 inches. In one preferred embodiment, thefoamed core has a “positive” hardness gradient (that is, the outer skinof the inner core is harder than its geometric center.)

For example, the geometric center hardness of the inner core(H_(inner core center)), as measured in Shore C units, is about 10 ShoreC or greater and preferably has a lower limit of about 10 or 16 or 20 or25 or 30 or 32 or 34 or 36 or 40 Shore C and an upper limit of about 42or 44 or 46 or 48 or 50 or 52 or 56 or 60 or 62 or 65 or 68 or 70 or 74or 78 or 80 Shore C. In one preferred version, the geometric centerhardness of the inner core (H_(inner core center)) is about 60 Shore C.When a flexible, relatively soft foam is used, the foam may have a ShoreA hardness of about 10 or greater, and preferably has a lower limit of15, 20, 25, 30, or 35 Shore A and an upper limit of about 60, 65, 70,80, 85, or 90 Shore A. In one preferred embodiment, the geometric centerhardness of the inner core is about 55 Shore A. TheH_(inner core center), as measured in Shore D units, is about 15 Shore Dor greater and more preferably within a range having a lower limit ofabout 15 or 18 or 20 or 22 or 25 or 28 or 30 or 32 or 36 or 40 or 44Shore D and an upper limit of about 45 or 48 or 50 or 52 or 55 or 58 or60 or 62 or 64 or 66 or 70 or 72 or 74 or 78 or 80 or 82 or 84 or 88 or90 Shore D. Meanwhile, the outer surface hardness of the inner core(H_(inner core surface)), as measured in Shore C, is about 20 Shore C orgreater and preferably has a lower limit of about 13 or 17 or 20 or 22or 24 or 28 or 30 or 32 or 35 or 36 or 40 or 42 or 44 or 46 or 48 or 50Shore C and an upper limit of about 52 or 55 or 58 or 60 or 62 or 64 or66 or 70 or 74 or 78 or 80 or 86 or 88 or 90 or 92 or 95 Shore C. Theouter surface hardness of the inner core (H_(inner core surface)), asmeasured in Shore D units, preferably has a lower limit of about 25 or28 or 30 or 32 or 36 or 40 or 44 Shore D and an upper limit of about 45or 48 or 50 or 52 or 55 or 58 or 60 or 62 or 64 or 66 or 70 or 74 or 78or 80 or 82 or 84 or 88 or 90 or 94 or 96 Shore D. In a particularembodiment, the H_(inner core center) is in the range of about 10 ShoreC to about 50 Shore C, and the H_(inner core surface) is in the range ofabout 13 Shore C to about 60 Shore C.

Density of the Inner Core

The foamed inner core preferably has a specific gravity of about 0.25 toabout 1.25 g/cc. That is, the density of the inner core (as measured atany point of the inner core structure) is preferably within the range ofabout 0.25 to about 1.25 g/cc. By the term, “specific gravity of theinner core” (“SG_(inner)”), it is generally meant the specific gravityof the inner core as measured at any point of the inner core structure.It should be understood, however, that the specific gravity values, astaken at different points of the inner core structure, may vary. Forexample, the foamed inner core may have a “positive” density gradient(that is, the outer surface (skin) of the inner core may have a densitygreater than the geometric center of the inner core.) In one preferredversion, the specific gravity of the geometric center of the inner core(SG_(center of inner core)) is less than 1.00 g/cc and more preferably0.90 g/cc or less. More particularly, in one version, the(SG_(center of inner core)) is in the range of about 0.10 to about 0.90g/cc. For example, the (SG_(center of inner core)) may be within a rangehaving a lower limit of about 0.10 or 0.15 of 0.20 or 0.24 or 0.25 or0.30 or 0.35 or 0.37 or 0.40 or 0.42 or 0.45 or 0.47 or 0.50 and anupper limit of about 0.60 or 0.65 or 0.70 or 0.74 or 0.78 or 0.80, or0.82 or 0.84 or 0.85 or 0.88 or 0.90 or 0.95 g/cc. Meanwhile, thespecific gravity of the outer surface (skin) of the inner core(SG_(skin of inner core)), in one preferred version, is greater thanabout 0.90 g/cc and more preferably greater than 1.00 g/cc. For example,the (SG_(skin of inner core)) may fall within the range of about 0.90 toabout 2.00. More particularly, in one version, the(SG_(skin of inner core)) may have a specific gravity with a lower limitof about 0.90 or 0.92 or 0.95 or 0.98 or 1.00 or 1.02 or 1.06 or 1.10 or1.12 or 1.15 or 1.18 and an upper limit of about 1.20 or 1.24 or 1.30 or1.32 or 1.35 or 1.38 or 1.40 or 1.44 or 1.50 or 1.60 or 1.65 or 1.70 or1.76 or 1.80 or 1.90 or 1.92 or 2.00. In other instances, the outer skinmay have a specific gravity of less than 0.90 g/cc. For example, thespecific gravity of the outer skin (SG_(skin of inner core)) may beabout 0.75 or 0.80 or 0.82 or 0.85 or 0.88 g/cc. In such instances,wherein both the (SG_(center of inner core)) and(SG_(skin of inner core)) are less than 0.90 g/cc, it is still preferredthat the (SG_(center of inner core)) is less than the(SG_(skin of inner core)).

Polyisocyanates and Polyols for Making the Polyurethane Foams

As discussed above, in one preferred embodiment, a foamed polyurethanecomposition is used to form the inner core. In general, the polyurethanecompositions contain urethane linkages formed by reacting an isocyanategroup (—N═C═O) with a hydroxyl group (OH). The polyurethanes areproduced by the reaction of multi-functional isocyanates containing twoor more isocyanate groups with a polyol having two or more hydroxylgroups. The formulation may also contain a catalyst, surfactant, andother additives.

In particular, the foam inner core of this invention may be preparedfrom a composition comprising an aromatic polyurethane, which ispreferably formed by reacting an aromatic diisocyanate with a polyol.Suitable aromatic diisocyanates that may be used in accordance with thisinvention include, for example, toluene 2,4-diisocyanate (TDI), toluene2,6-diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI),2,4′-methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyldiisocyanate (PMDI), p-phenylene diisocyanate (PPDI), m-phenylenediisocyanate (PDI), naphthalene 1,5-diisocyanate (NDI), naphthalene2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and homopolymersand copolymers and blends thereof. The aromatic isocyanates are able toreact with the hydroxyl or amine compounds and form a durable and toughpolymer having a high melting point. The resulting polyurethanegenerally has good mechanical strength and tear-resistance.

Alternatively, the foamed composition of the inner core may be preparedfrom a composition comprising aliphatic polyurethane, which ispreferably formed by reacting an aliphatic diisocyanate with a polyol.Suitable aliphatic diisocyanates that may be used in accordance withthis invention include, for example, isophorone diisocyanate (IPDI),1,6-hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethanediisocyanate (“H₁₂ MDI”), meta-tetramethylxylyene diisocyanate (TMXDI),trans-cyclohexane diisocyanate (CHDI),1,3-bis(isocyanatomethyl)cyclohexane;1,4-bis(isocyanatomethyl)cyclohexane; and homopolymers and copolymersand blends thereof. The resulting polyurethane generally has good lightand thermal stability. Preferred polyfunctional isocyanates include4,4′-methylene diphenyl diisocyanate (MDI), 2,4′-methylene diphenyldiisocyanate (MDI), and polymeric MDI having a functionality in therange of 2.0 to 3.5 and more preferably 2.2 to 2.5.

Any suitable polyol may be used to react with the polyisocyanate inaccordance with this invention. Exemplary polyols include, but are notlimited to, polyether polyols, hydroxy-terminated polybutadiene(including partially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, and polycarbonate polyols. In one preferredembodiment, the polyol includes polyether polyol. Examples include, butare not limited to, polytetramethylene ether glycol (PTMEG),polyethylene propylene glycol, polyoxypropylene glycol, and mixturesthereof. The hydrocarbon chain can have saturated or unsaturated bondsand substituted or unsubstituted aromatic and cyclic groups. Preferably,the polyol of the present invention includes PTMEG.

As discussed further below, chain extenders (curing agents) are added tothe mixture to build-up the molecular weight of the polyurethanepolymer. In general, hydroxyl-terminated curing agents, amine-terminatedcuring agents, and mixtures thereof are used.

A catalyst may be employed to promote the reaction between theisocyanate and polyol compounds. Suitable catalysts include, but are notlimited to, bismuth catalyst; zinc octoate; tin catalysts such asbis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin(II) chloride, tin (IV) chloride, bis-butyltin dimethoxide,dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctylmercaptoacetate; amine catalysts such as triethylenediamine,triethylamine, tributylamine, 1,4-diaza(2,2,2)bicyclooctane,tetramethylbutane diamine, bis[2-dimethylaminoethyl]ether,N,N-dimethylaminopropylamine, N,N-dimethylcyclohexylamine,N,N,N′,N′,N″-pentamethyldiethylenetriamine, diethanolamine,dimethtlethanolamine, N-[2-(dimethylamino)ethyl]-N-methylethanolamine,N-ethylmorpholine, 3-dimethylamino-N,N-dimethylpropionamide, andN,N′,N″-dimethylaminopropylhexahydrotriazine; organic acids such asoleic acid and acetic acid; delayed catalysts; and mixtures thereof.Zirconium-based catalysts such as, for example, bis(2-dimethylaminoethyl) ether; mixtures of zinc complexes and amine compounds suchas KKAT™ XK 614, available from King Industries; and amine catalystssuch as Niax™ A-2 and A-33, available from Momentive SpecialtyChemicals, Inc. are particularly preferred. The catalyst is preferablyadded in an amount sufficient to catalyze the reaction of the componentsin the reactive mixture. In one embodiment, the catalyst is present inan amount from about 0.001 percent to about 1 percent, and preferably0.1 to 0.5 percent, by weight of the composition.

In one preferred embodiment, as described above, water is used as thefoaming agent—the water reacts with the polyisocyanate compound(s) andforms carbon dioxide gas which induces foaming of the mixture. Thereaction rate of the water and polyisocyanate compounds affects howquickly the foam is formed as measured per reaction profile propertiessuch as cream time, gel time, and rise time of the foam.

The hydroxyl chain-extending (curing) agents are preferably selectedfrom the group consisting of ethylene glycol; diethylene glycol;polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol;2-methyl-1,4-butanediol; monoethanolamine; diethanolamine;triethanolamine; monoisopropanolamine; diisopropanolamine; dipropyleneglycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol;1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol;trimethylolpropane; cyclohexyldimethylol; triisopropanolamine;N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycolbis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol;1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol;1,3-bis-[2-(2-hydroxyethoxy) ethoxy]cyclohexane;1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}cyclohexane;trimethylolpropane; polytetramethylene ether glycol (PTMEG), preferablyhaving a molecular weight from about 250 to about 3900; and mixturesthereof. Di, tri, and tetra-functional polycaprolactone diols such as,2-oxepanone polymer initiated with 1,4-butanediol,2-ethyl-2-(hydroxymethyl)-1,3-propanediol, or2,2-bis(hydroxymethyl)-1,3-propanediol such, may be used.

Suitable amine chain-extending (curing) agents that can be used inchain-extending the polyurethane prepolymer include, but are not limitedto, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-dianiline or “MDA”), m-phenylenediamine,p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene,3,5-diethyl-(2,4- or 2,6-) toluenediamine or “DETDA”,3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane,3,3′-diethyl-5,5′-dimethyl4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)),3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-chloroaniline) or “MOCA”),3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2,6-diethylaniline),2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”),3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”),3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane,3,3′-dichloro-4,4′-diamino-diphenylmethane,4,4′-methylene-bis(2,3-dichloroaniline) (i.e.,2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”),4,4′-bis(sec-butylamino)-diphenylmethane,N,N′-dialkylamino-diphenylmethane,trimethyleneglycol-di(p-aminobenzoate),polyethyleneglycol-di(p-aminobenzoate),polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such asethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylenediamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine, imino-bis(propylamine), imido-bis(propylamine),methylimino-bis(propylamine) (i.e.,N-(3-aminopropyl)-N-methyl-1,3-propanediamine),1,4-bis(3-aminopropoxy)butane (i.e.,3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine),diethyleneglycol-bis(propylamine) (i.e.,diethyleneglycol-di(aminopropyl)ether),4,7,10-trioxatridecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane,1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene) diamines, 1,3-or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophoronediamine, 4,4′-diamino-dicyclohexylmethane,3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane,3,3′-dichloro-4,4′-diamino-dicyclohexylmethane,N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines,3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane,polyoxypropylene diamines,3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane,polytetramethylene ether diamines,3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (i.e.,4,4′-methylene-bis(2,6-diethylaminocyclohexane)),3,3′-dichloro-4,4′-diamino-dicyclohexylmethane,2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane,(ethylene oxide)-capped polyoxypropylene ether diamines,2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane,4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such asdiethylene triamine, dipropylene triamine, (propylene oxide)-basedtriamines (i.e., polyoxypropylene triamines),N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine), glycerin-basedtriamines, (all saturated); tetramines such asN,N′-bis(3-aminopropyl)ethylene diamine (i.e., N₄-amine) (bothsaturated), triethylene tetramine; and other polyamines such astetraethylene pentamine (also saturated). One suitable amine-terminatedchain-extending agent is Ethacure 300™ (dimethylthiotoluenediamine or amixture of 2,6-diamino-3,5-dimethylthiotoluene and2,4-diamino-3,5-dimethylthiotoluene.) The amine curing agents used aschain extenders normally have a cyclic structure and a low molecularweight (250 or less).

When a hydroxyl-terminated curing agent is used, the resultingpolyurethane composition contains urethane linkages. On the other hand,when an amine-terminated curing agent is used, any excess isocyanategroups will react with the amine groups in the curing agent. Theresulting polyurethane composition contains urethane and urea linkagesand may be referred to as a polyurethane/urea hybrid.

Outer Core Layer Composition

As discussed above, the inner core is made preferably from a foamedcomposition. In one embodiment, the outer core layer is formed from anon-foamed thermoset composition and more preferably from a non-foamedthermoset rubber composition. In another embodiment, the outer corelayer is formed from non-foamed thermoplastic composition.

Suitable thermoset rubber materials for forming the outer core layerinclude, but are not limited to, polybutadiene, polyisoprene, ethylenepropylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”) rubber,styrene-butadiene rubber, styrenic block copolymer rubbers (such as“SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S” is styrene,“I” is isobutylene, and “B” is butadiene), polyalkenamers such as, forexample, polyoctenamer, butyl rubber, halobutyl rubber, polystyreneelastomers, polyethylene elastomers, polyurethane elastomers, polyureaelastomers, metallocene-catalyzed elastomers and plastomers, copolymersof isobutylene and p-alkylstyrene, halogenated copolymers of isobutyleneand p-alkylstyrene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber,acrylonitrile chlorinated isoprene rubber, and blends of two or morethereof. Preferably, the outer core layer is formed from a polybutadienerubber composition.

The thermoset rubber composition may be cured using conventional curingprocesses. Suitable curing processes include, for example,peroxide-curing, sulfur-curing, high-energy radiation, and combinationsthereof. Preferably, the rubber composition contains a free-radicalinitiator selected from organic peroxides, high energy radiation sourcescapable of generating free-radicals, and combinations thereof. In onepreferred version, the rubber composition is peroxide-cured. Suitableorganic peroxides include, but are not limited to, dicumyl peroxide;n-butyl-4,4-di(t-butylperoxy) valerate;1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoylperoxide; t-butyl hydroperoxide; and combinations thereof. In aparticular embodiment, the free radical initiator is dicumyl peroxide,including, but not limited to Perkadox® BC, commercially available fromAkzo Nobel. Peroxide free-radical initiators are generally present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the total rubber, or an amount within the range having alower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5parts or 2.5 parts or 5 parts by weight per 100 parts of the totalrubbers, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6parts or 10 parts or 15 parts by weight per 100 parts of the totalrubber. Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term, “parts per hundred,” also known as“phr” or “pph” is defined as the number of parts by weight of aparticular component present in a mixture, relative to 100 parts byweight of the polymer component. Mathematically, this can be expressedas the weight of an ingredient divided by the total weight of thepolymer, multiplied by a factor of 100.

The rubber compositions may further include a reactive cross-linkingco-agent. Suitable co-agents include, but are not limited to, metalsalts of unsaturated carboxylic acids having from 3 to 8 carbon atoms;unsaturated vinyl compounds and polyfunctional monomers (e.g.,trimethylolpropane trimethacrylate); phenylene bismaleimide; andcombinations thereof. Particular examples of suitable metal saltsinclude, but are not limited to, one or more metal salts of acrylates,diacrylates, methacrylates, and dimethacrylates, wherein the metal isselected from magnesium, calcium, zinc, aluminum, lithium, and nickel.In a particular embodiment, the co-agent is selected from zinc salts ofacrylates, diacrylates, methacrylates, and dimethacrylates. In anotherparticular embodiment, the agent is zinc diacrylate (ZDA). When theco-agent is zinc diacrylate and/or zinc dimethacrylate, the co-agent istypically included in the rubber composition in an amount within therange having a lower limit of 1 or 5 or 10 or 15 or 19 or 20 parts byweight per 100 parts of the total rubber, and an upper limit of 24 or 25or 30 or 35 or 40 or 45 or 50 or 60 parts by weight per 100 parts of thebase rubber.

Radical scavengers such as a halogenated organosulfur, organicdisulfide, or inorganic disulfide compounds may be added to the rubbercomposition. These compounds also may function as “soft and fastagents.” As used herein, “soft and fast agent” means any compound or ablend thereof that is capable of making a core: 1) softer (having alower compression) at a constant “coefficient of restitution” (COR);and/or 2) faster (having a higher COR at equal compression), whencompared to a core equivalently prepared without a soft and fast agent.Preferred halogenated organosulfur compounds include, but are notlimited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zincpentachlorothiophenol (ZnPCTP). Using PCTP and ZnPCTP in golf ball innercores helps produce softer and faster inner cores. The PCTP and ZnPCTPcompounds help increase the resiliency and the coefficient ofrestitution of the core. In a particular embodiment, the soft and fastagent is selected from ZnPCTP, PCTP, ditolyl disulfide, diphenyldisulfide, dixylyl disulfide, 2-nitroresorcinol, and combinationsthereof.

The rubber composition also may include filler(s) such as materialsselected from carbon black, nanoclays (e.g., Cloisite® and Nanofil®nanoclays, commercially available from Southern Clay Products, Inc., andNanomax® and Nanomer® nanoclays, commercially available from Nanocor,Inc.), talc (e.g., Luzenac HAR® high aspect ratio talcs, commerciallyavailable from Luzenac America, Inc.), glass (e.g., glass flake, milledglass, and microglass), mica and mica-based pigments (e.g., Iriodin®pearl luster pigments, commercially available from The Merck Group), andcombinations thereof. Metal fillers such as, for example, particulate;powders; flakes; and fibers of copper, steel, brass, tungsten, titanium,aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc,barium, bismuth, bronze, silver, gold, and platinum, and alloys andcombinations thereof also may be added to the rubber composition toadjust the specific gravity of the composition as needed.

In addition, the rubber compositions may include antioxidants to preventthe breakdown of the elastomers. Also, processing aids such as highmolecular weight organic acids and salts thereof may be added to thecomposition. Suitable organic acids are aliphatic organic acids,aromatic organic acids, saturated mono-functional organic acids,unsaturated monofunctional organic acids, multi-unsaturatedmono-functional organic acids, and dimerized derivatives thereof.Particular examples of suitable organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid,myristic acid, benzoic acid, palmitic acid, phenylacetic acid,naphthalenoic acid, and dimerized derivatives thereof. The organic acidsare aliphatic, mono-functional (saturated, unsaturated, ormulti-unsaturated) organic acids. Salts of these organic acids may alsobe employed. The salts of organic acids include the salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium, salts of fatty acids, particularly stearic,behenic, erucic, oleic, linoelic or dimerized derivatives thereof. It ispreferred that the organic acids and salts of the present invention berelatively non-migratory (they do not bloom to the surface of thepolymer under ambient temperatures) and non-volatile (they do notvolatilize at temperatures required for melt-blending.) Otheringredients such as accelerators (for example, tetra methylthiuram),processing aids, dyes and pigments, wetting agents, surfactants,plasticizers, coloring agents, fluorescent agents, chemical blowing andfoaming agents, defoaming agents, stabilizers, softening agents, impactmodifiers, antiozonants, as well as other additives known in the art maybe added to the rubber composition.

Examples of commercially-available polybutadiene rubbers that can beused in accordance with this invention, include, but are not limited to,BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand;SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland,Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Incof Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber(JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221,available from Lanxess Corp. of Pittsburgh, Pa.; BR1208, available fromLG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L,BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. ofTokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, andEUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY)Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co.,Ltd. Of Seoul, South Korea; DIENE 55NF, 70AC, and 320 AC, available fromFirestone Polymers of Akron, Ohio; and PBR-Nd Group II and Group III,available from Nizhnekamskneftekhim, Inc. of Nizhnekamsk, TartarstanRepublic.

The polybutadiene rubber is used in an amount of at least about 5% byweight based on total weight of composition and is generally present inan amount of about 5% to about 100%, or an amount within a range havinga lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upperlimit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, theconcentration of polybutadiene rubber is about 40 to about 95 weightpercent. If desirable, lesser amounts of other thermoset materials maybe incorporated into the base rubber. Such materials include the rubbersdiscussed above, for example, cis-polyisoprene, trans-polyisoprene,balata, polychloroprene, polynorbornene, polyoctenamer, polypentenamer,butyl rubber, EPR, EPDM, styrene-butadiene, and the like.

Suitable thermoplastic materials for forming the outer core layerinclude, but are not limited to, ionomer compositions containing acidgroups that are at least partially-neutralized. Suitable ionomercompositions include partially-neutralized ionomers andhighly-neutralized ionomers (HNPs), including ionomers formed fromblends of two or more partially-neutralized ionomers, blends of two ormore highly-neutralized ionomers, and blends of one or morepartially-neutralized ionomers with one or more highly-neutralizedionomers. For purposes of the present disclosure, “HNP” refers to anacid copolymer after at least 70% of all acid groups present in thecomposition are neutralized. Preferred ionomers are salts of O/X- andO/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softeningmonomer. O is preferably selected from ethylene and propylene. X ispreferably selected from methacrylic acid, acrylic acid, ethacrylicacid, crotonic acid, and itaconic acid. Methacrylic acid and acrylicacid are particularly preferred. Y is preferably selected from (meth)acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1to 8 carbon atoms, including, but not limited to, n-butyl (meth)acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl(meth) acrylate.

Preferred O/X and O/X/Y-type copolymers include, without limitation,ethylene acid copolymers, such as ethylene/(meth)acrylic acid,ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylicacid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acidmono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate,ethylene/(meth)acrylic acid/methyl (meth)acrylate,ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and thelike. The term, “copolymer,” as used herein, includes polymers havingtwo types of monomers, those having three types of monomers, and thosehaving more than three types of monomers. Preferred α,β-ethylenicallyunsaturated mono- or dicarboxylic acids are (meth) acrylic acid,ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconicacid. (Meth) acrylic acid is most preferred. As used herein, “(meth)acrylic acid” means methacrylic acid and/or acrylic acid. Likewise,“(meth) acrylate” means methacrylate and/or acrylate.

Suitable acid polymers for forming the ionomer composition also includeacid polymers that are already partially neutralized. Examples ofsuitable partially neutralized acid polymers include, but are notlimited to, Surlyn® ionomers, commercially available from E. I. du Pontde Nemours and Company; AClyn® ionomers, commercially available fromHoneywell International Inc.; and Iotek® ionomers, commerciallyavailable from ExxonMobil Chemical Company. Also suitable are DuPont®HPF 1000 and DuPont® HPF 2000, ionomeric materials commerciallyavailable from E. I. du Pont de Nemours and Company. In someembodiments, very low modulus ionomer- (“VLMI-”) type ethylene-acidpolymers are particularly suitable for forming the ionomer composition,such as Surlyn® 6320, Surlyn® 8120, Surlyn® 8320, and Surlyn® 9320,commercially available from E. I. du Pont de Nemours and Company.

The α-olefin is typically present in the O/X or O/X/Y-type copolymer inan amount of 15 wt. % or greater, or 25 wt. % or greater, or 40 wt. % orgreater, or 60 wt. % or greater, based on the total weight of the acidcopolymer. The acid is typically present in the acid copolymer in anamount of 6 wt. % or greater, or 9 wt. % or greater, or 10 wt. % orgreater, or 11 wt. % or greater, or 15 wt. % or greater, or 16 wt. % orgreater, or in an amount within a range having a lower limit of 1 or 4or 5 or 6 or 8 or 10 or 11 or 12 or 15 or 16 or 20 wt. % and an upperlimit of 15 or 16 or 17 or 19 or 20 or 20.5 or 21 or 25 or 26 or 30 or35 or 40 wt. %, based on the total weight of the acid copolymer. Theoptional softening monomer is typically present in the acid copolymer inan amount within a range having a lower limit of 0 or 1 or 3 or 5 or 11or 15 or 20 wt. % and an upper limit of 23 or 25 or 30 or 35 or 50 wt.%, based on the total weight of the acid copolymer.

Additional suitable acid polymers are more fully described, for example,in U.S. Pat. Nos. 5,691,418, 6,562,906, 6,653,382, 6,777,472, 6,762,246,6,815,480, and 6,953,820 and U.S. Patent Application Publication Nos.2005/0148725, 2005/0049367, 2005/0020741, 2004/0220343, and2003/0130434, the entire disclosures of which are hereby incorporatedherein by reference.

The O/X or O/X/Y-type copolymer is at least partially neutralized with acation source, optionally in the presence of a high molecular weightorganic acid, such as those disclosed in U.S. Pat. No. 6,756,436, theentire disclosure of which is hereby incorporated herein by reference,such that at least 70%, preferably at least 80%, more preferably atleast 90%, more preferably at least 95%, and even more preferably 100%,of all acid groups present are neutralized. In a particular embodiment,the cation source is present in an amount sufficient to neutralize,theoretically, greater than 100%, or 105% or greater, or 110% orgreater, or 115% or greater, or 120% or greater, or 125% or greater, or200% or greater, or 250% or greater of all acid groups present in thecomposition. The acid copolymer can be reacted with the optional highmolecular weight organic acid and the cation source simultaneously, orprior to the addition of the cation source.

Suitable cation sources include, but are not limited to, metal ionsources, such as compounds of alkali metals, alkaline earth metals,transition metals, and rare earth elements; ammonium salts and monoaminesalts; and combinations thereof. Preferred cation sources are compoundsof magnesium, sodium, potassium, cesium, calcium, barium, manganese,copper, zinc, lead, tin, aluminum, nickel, chromium, lithium, and rareearth metals. Methods of preparing ionomers, and the acid polymers onwhich ionomers are based, are disclosed, for example, in U.S. Pat. Nos.3,264,272, and 4,351,931, and U.S. Patent Application Publication No.2002/0013413.

Suitable high molecular weight organic acids are aliphatic organicacids, aromatic organic acids, saturated monofunctional organic acids,unsaturated monofunctional organic acids, multi-unsaturatedmonofunctional organic acids, and dimerized derivatives thereof.Particular examples of suitable organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid,myristic acid, benzoic acid, palmitic acid, phenylacetic acid,naphthalenoic acid, dimerized derivatives thereof, and combinationsthereof. Salts of high molecular weight organic acids comprise thesalts, particularly the barium, lithium, sodium, zinc, bismuth,chromium, cobalt, copper, potassium, stontium, titanium, tungsten,magnesium, and calcium salts, of aliphatic organic acids, aromaticorganic acids, saturated monofunctional organic acids, unsaturatedmonofunctional organic acids, multi-unsaturated monofunctional organicacids, dimerized derivatives thereof, and combinations thereof. Suitableorganic acids and salts thereof are more fully described, for example,in U.S. Pat. No. 6,756,436, the entire disclosure of which is herebyincorporated herein by reference. In a particular embodiment, the HNPcomposition comprises an organic acid salt in an amount of 20 phr orgreater, or 25 phr or greater, or 30 phr or greater, or 35 phr orgreater, or 40 phr or greater.

The ionomer composition optionally comprises at least one additionalpolymer component selected from partially neutralized ionomers asdisclosed, for example, in U.S. Patent Application Publication No.2006/0128904, the entire disclosure of which is hereby incorporatedherein by reference; bimodal ionomers, such as those disclosed in U.S.Patent Application Publication No. 2004/0220343 and U.S. Pat. Nos.6,562,906, 6,762,246, 7,273,903, 8,193,283, 8,410,219, and 8,410,220,the entire disclosures of which are hereby incorporated herein byreference, and particularly Surlyn® AD 1043, 1092, and 1022 ionomerresins, commercially available from E. I. du Pont de Nemours andCompany; ionomers modified with rosins, such as those disclosed in U.S.Patent Application Publication No. 2005/0020741, the entire disclosureof which is hereby incorporated by reference; soft and resilientethylene copolymers, such as those disclosed U.S. Patent ApplicationPublication No. 2003/0114565, the entire disclosure of which is herebyincorporated herein by reference; polyolefins, such as linear, branched,or cyclic, C₂-C₄₀ olefins, particularly polymers comprising ethylene orpropylene copolymerized with one or more C₂-C₄₀ olefins, C₃-C₂₀α-olefins, or C₃-C₁₀ α-olefins; polyamides; polyesters; polyethers;polycarbonates; polysulfones; polyacetals; polylactones;acrylonitrile-butadiene-styrene resins; polyphenylene oxide;polyphenylene sulfide; styrene-acrylonitrile resins; styrene maleicanhydride; polyimides; aromatic polyketones; ionomers and ionomericprecursors, acid copolymers, and conventional HNPs, such as thosedisclosed in U.S. Pat. Nos. 6,756,436, 6,894,098, and 6,953,820, theentire disclosures of which are hereby incorporated herein by reference;polyurethanes; grafted and non-grafted metallocene-catalyzed polymers,such as single-site catalyst polymerized polymers, high crystalline acidpolymers, cationic ionomers, and combinations thereof; natural andsynthetic rubbers, including, but not limited to, ethylene propylenerubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic blockcopolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where“S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber,halobutyl rubber, copolymers of isobutylene and para-alkylstyrene,halogenated copolymers of isobutylene and para-alkylstyrene, naturalrubber, polyisoprene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber (such as ethylene-alkyl acrylatesand ethylene-alkyl methacrylates, and, more specifically, ethylene-ethylacrylate, ethylene-methyl acrylate, and ethylene-butyl acrylate),chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber,and polybutadiene rubber (cis and trans). Additional suitable blendpolymers include those described in U.S. Pat. No. 5,981,658, for exampleat column 14, lines 30 to 56, the entire disclosure of which is herebyincorporated herein by reference. The blend may be produced bypost-reactor blending, by connecting reactors in series to make reactorblends, or by using more than one catalyst in the same reactor toproduce multiple species of polymer. The polymers may be mixed prior tobeing put into an extruder, or they may be mixed in an extruder. In aparticular embodiment, the ionomer composition comprises an acidcopolymer and an additional polymer component, wherein the additionalpolymer component is a non-acid polymer present in an amount of greaterthan 50 wt %, or an amount within a range having a lower limit of 50 or55 or 60 or 65 or 70 and an upper limit of 80 or 85 or 90, based on thecombined weight of the acid copolymer and the non-acid polymer. Inanother particular embodiment, the ionomer composition comprises an acidcopolymer and an additional polymer component, wherein the additionalpolymer component is a non-acid polymer present in an amount of lessthan 50 wt %, or an amount within a range having a lower limit of 10 or15 or 20 or 25 or 30 and an upper limit of 40 or 45 or 50, based on thecombined weight of the acid copolymer and the non-acid polymer.

Suitable HNP compositions are further disclosed, for example, in U.S.Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,815,480, 6,894,098,6,919,393, 6,953,820, 6,994,638, 7,375,151, the entire disclosures ofwhich are hereby incorporated herein by reference.

Non-limiting examples of suitable commercially available ionomers andother thermoplastic materials that can be used in accordance with thisinvention are Surlyn® ionomers and DuPont® HPF 1000 and HPF 2000 highlyneutralized polymers, commercially available from E. I. du Pont deNemours and Company; Clarix® ionomers, commercially available from A.Schulman, Inc.; Iotek® ionomers, commercially available from ExxonMobilChemical Company; and Amplify® IO ionomers, commercially available fromThe Dow Chemical Company; Amplify® GR functional polymers and Amplify®TY functional polymers, commercially available from The Dow ChemicalCompany; Fusabond® functionalized polymers, commercially available fromE. I. du Pont de Nemours and Company; Exxelor® maleic anhydride graftedpolymers, commercially available from ExxonMobil Chemical Company;ExxonMobil® PP series polypropylene impact copolymers, commerciallyavailable from ExxonMobil Chemical Company; Vistamaxx® propylene-basedelastomers, commercially available from ExxonMobil Chemical Company;Exact® plastomers, commercially available from ExxonMobil ChemicalCompany; Santoprene® thermoplastic vulcanized elastomers, commerciallyavailable from ExxonMobil Chemical Company; Kraton® styrenic blockcopolymers, commercially available from Kraton Performance PolymersInc.; Septon® styrenic block copolymers, commercially available fromKuraray Co., Ltd.; Lotader® ethylene acrylate based polymers,commercially available from Arkema Corporation; Polybond® graftedpolyethylenes and polypropylenes, commercially available from ChemturaCorporation; Pebax® polyether and polyester amides, commerciallyavailable from Arkema Inc.; polyester-based thermoplastic elastomers,such as Hytrel® polyester elastomers, commercially available from E. I.du Pont de Nemours and Company, and Riteflex® polyester elastomers,commercially available from Ticona; Estane® thermoplastic polyurethanes,commercially available from The Lubrizol Corporation; Grivory®polyamides and Grilamid® polyamides, commercially available from EMSGrivory; Zytel® polyamide resins and Elvamide® nylon multipolymerresins, commercially available from E. I. du Pont de Nemours andCompany; Elvaloy® acrylate copolymer resins, commercially available fromE. I. du Pont de Nemours and Company; Elastollan® polyurethane-basedthermoplastic elastomers, commercially available from BASF; Xylex®polycarbonate/polyester blends, commercially available from SABICInnovative Plastics; and combinations of two or more thereof.

As discussed above, the acid is typically present in the O/X orO/X/Y-type copolymer in an amount of 6 wt. % or greater. “Low acid” and“high acid” ionomeric copolymers, as well as blends of such ionomers,may be used. In general, low acid ionomers are considered to be thosecontaining 16 wt. % or less of acid moieties, whereas high acid ionomersare considered to be those containing greater than 16 wt. % of acidmoieties. The acidic groups in the acid copolymers are partially ortotally-neutralized with a cation source. Suitable cation sourcesinclude metal cations and salts thereof, organic amine compounds,ammonium, and combinations thereof. Suitable cation sources include, forexample, metal cations and salts thereof, wherein the metal ispreferably lithium, sodium, potassium, magnesium, calcium, barium, lead,tin, zinc, aluminum, manganese, nickel, chromium, copper, or acombination thereof. The metal cation salts provide the cations capableof neutralizing (at varying levels) the carboxylic acids of the ethyleneacid copolymer and fatty acids, if present, as discussed further below.These include, for example, the sulfate, carbonate, acetate, oxide, orhydroxide salts of lithium, sodium, potassium, magnesium, calcium,barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper,or a combination thereof. Preferred metal cation salts are calcium andmagnesium-based salts. High surface area cation particles such as microand nano-scale cation particles are preferred. The amount of cation usedin the composition is readily determined based on desired level ofneutralization.

For example, olefin acid copolymer ionomer resins having acid groupsthat are neutralized from about 10 percent or greater may be used. Inone ionomer composition, the acid groups are partially-neutralized. Thatis, the neutralization level is from about 10% to about 70%, morepreferably 20% to 60%, and most preferably 30 to 50%. These ionomercompositions, containing acid groups neutralized to 70% or less, may bereferred to ionomers having relatively low neutralization levels orpartial-neutralization. On the other hand, the ionomer composition maycontain acid groups that are highly or fully-neutralized. In these HNPs,the neutralization level is greater than 70%, preferably at least 90%,and even more preferably at least 100%. In another embodiment, an excessamount of neutralizing agent, that is, an amount greater than thestoichiometric amount needed to neutralize the acid groups, may be used.That is, the acid groups may be neutralized to 100% or greater, forexample 110% or 120% or greater.

When the α-olefin monomer is ethylene, such copolymers are referred toherein as E/X-type copolymers and when a softening monomer is included,such copolymers are referred to herein as E/X/Y-type copolymers, whereinE is ethylene; X is a C₃ to C₈ α,β-ethylenically unsaturated mono- ordicarboxylic acid; and Y is a softening monomer. The softening monomeris typically an alkyl (meth) acrylate, wherein the alkyl groups havefrom 1 to 8 carbon atoms. Preferred E/X/Y-type copolymers are thosewherein X is (meth) acrylic acid and/or Y is selected from (meth)acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl(meth) acrylate, and ethyl (meth) acrylate. More preferred E/X/Y-typecopolymers are ethylene/(meth) acrylic acid/n-butyl acrylate,ethylene/(meth) acrylic acid/methyl acrylate, and ethylene/(meth)acrylic acid/ethyl acrylate.

The amount of ethylene in the E/X and E/X/Y-type copolymers is typicallyat least 15 wt. %, preferably at least 25 wt. %, more preferably least40 wt. %, and even more preferably at least 60 wt. %, based on totalweight of the copolymer. The amount of C₃ to C₈ α,β-ethylenicallyunsaturated mono- or dicarboxylic acid in the ethylene acid copolymer istypically from 1 wt. % to 35 wt. %, preferably from 5 wt. % to 30 wt. %,more preferably from 5 wt. % to 25 wt. %, and even more preferably from10 wt. % to 20 wt. %, based on total weight of the copolymer. The amountof optional softening monomer in the ethylene acid copolymer istypically from 0 wt. % to 50 wt. %, preferably from 5 wt. % to 40 wt. %,more preferably from 10 wt. % to 35 wt. %, and even more preferably from20 wt. % to 30 wt. %, based on total weight of the copolymer. Asdiscussed above, “low acid” and “high acid” ionomeric polymers, as wellas blends of such ionomers, may be used. In general, low acid ionomersare considered to be those containing 16 wt. % or less of acid moieties,whereas high acid ionomers are considered to be those containing greaterthan 16 wt. % of acid moieties.

As discussed above, the acidic groups in the E/X and E/X/Y-typecopolymer ionomers are partially or totally neutralized with a cationsource. Suitable cation sources include metal cations and salts thereof,organic amine compounds, ammonium, and combinations thereof. Preferredcation sources are metal cations and salts thereof, wherein the metal ispreferably lithium, sodium, potassium, magnesium, calcium, barium, lead,tin, zinc, aluminum, manganese, nickel, chromium, copper, or acombination thereof. The metal cation salts provide the cations capableof neutralizing (at varying levels) the carboxylic acids of the ethyleneacid copolymer and fatty acids, if present, as discussed further below.These include, for example, the sulfate, carbonate, acetate, oxide, orhydroxide salts of lithium, sodium, potassium, magnesium, calcium,barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper,or a combination thereof. Preferred metal cation salts are calcium andmagnesium-based salts. High surface area cation particles such as microand nano-scale cation particles are preferred. The amount of cation usedin the composition is readily determined based on desired level ofneutralization.

For example, ethylene acid copolymers having acid groups that areneutralized from about 10 percent or greater may be used. In oneethylene acid copolymer composition, the acid groups arepartially-neutralized. That is, the neutralization level is from about10% to about 70%, more preferably 20% to 60%, and most preferably 30 to50%. These ethylene acid copolymer compositions, containing acid groupsneutralized to 70% or less, may be referred to ionomers havingrelatively low neutralization levels or partial-neutralization. On theother hand, the ethylene acid copolymer composition may contain acidgroups that are highly or fully-neutralized. In these HNPs, theneutralization level is greater than 70%, preferably at least 90%, andeven more preferably at least 100%. In another embodiment, an excessamount of neutralizing agent, that is, an amount greater than thestoichiometric amount needed to neutralize the acid groups, may be used.That is, the acid groups may be neutralized to 100% or greater, forexample 110% or 120% or greater. In one preferred embodiment, a highacid ethylene acid copolymer containing about 19 to 20 wt. % methacrylicor acrylic acid is neutralized with zinc and sodium cations to a 95%neutralization level.

“Ionic plasticizers” such as organic acids or salts of organic acids,particularly fatty acids, may be added to any of the ionomer resins ifneeded. Such ionic plasticizers are used to make conventional ionomercomposition more processable as described in Rajagopalan et al., U.S.Pat. No. 6,756,436, the disclosure of which is hereby incorporated byreference. In one preferred embodiment, the thermoplastic ionomercomposition, containing acid groups neutralized to 70% or less, does notinclude a fatty acid or salt thereof, or any other ionic plasticizer. Onthe other hand, the thermoplastic ionomer composition, containing acidgroups neutralized to greater than 70%, includes an ionic plasticizer,particularly a fatty acid or salt thereof. For example, the ionicplasticizer may be added in an amount of 0.5 to 10 pph, more preferably1 to 5 pph. The organic acids may be aliphatic, mono- ormulti-functional (saturated, unsaturated, or multi-unsaturated) organicacids. Salts of these organic acids may also be employed. Suitable fattyacid salts include, for example, metal stearates, laureates, oleates,palmitates, pelargonates, and the like. For example, fatty acid saltssuch as zinc stearate, calcium stearate, magnesium stearate, bariumstearate, and the like can be used. The salts of fatty acids aregenerally fatty acids neutralized with metal ions. The metal cationsalts provide the cations capable of neutralizing (at varying levels)the carboxylic acid groups of the fatty acids. Examples include thesulfate, carbonate, acetate and hydroxide salts of metals such asbarium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper,potassium, strontium, titanium, tungsten, magnesium, cesium, iron,nickel, silver, aluminum, tin, or calcium, and blends thereof. It ispreferred the organic acids and salts be relatively non-migratory (theydo not bloom to the surface of the polymer under ambient temperatures)and non-volatile (they do not volatilize at temperatures required formelt-blending).

As noted above, the final ionomer compositions may contain additionalmaterials such as, for example, a small amount of ionic plasticizer,which is particularly effective at improving the processability ofhighly-neutralized ionomers. For example, the ionic plasticizer may beadded in an amount of 0.5 to 10 pph, more preferably 1 to 5 pph. Inaddition to the fatty acids and salts of fatty acids discussed above,other suitable ionic plasticizers include, for example, polyethyleneglycols, waxes, bis-stearamides, minerals, and phthalates. In anotherembodiment, an amine or pyridine compound is used, preferably inaddition to a metal cation. Suitable examples include, for example,ethylamine, methylamine, diethylamine, tert-butylamine, dodecylamine,and the like.

The ionomer compositions may contain a wide variety of fillers and someof these fillers may be used to adjust the specific gravity of thecomposition as needed. High surface-area fillers that have an affinityfor the acid groups in ionomer may be used. In particular, fillers suchas particulate, fibers, or flakes having cationic nature such that theymay also contribute to the neutralization of the ionomer are suitable.For example, aluminum oxide, zinc oxide, tin oxide, barium sulfate, zincsulfate, calcium oxide, calcium carbonate, zinc carbonate, bariumcarbonate, tungsten, tungsten carbide, and lead silicate fillers may beused. Also, silica, fumed silica, and precipitated silica, such as thosesold under the tradename, HISIL™, from PPG Industries, carbon black,carbon fibers, and nano-scale materials such as nanotubes, nanoflakes,nanofillers, and nanoclays may be used. Relatively heavy-weight fillersalso may be added to the ionomer compositions including, but not limitedto, particulate, powders, fibers and flakes of heavy metals such ascopper, nickel, tungsten, brass, steel, magnesium, molybdenum, cobalt,lead, tin, silver, gold, and platinum, and alloys thereof. Steelmaterials also can be added. In other instances, it may be desirable toadd relatively light-weight metals such as titanium and aluminum alloysthereof. Other additives and fillers include, but are not limited to,chemical blowing and foaming agents, optical brighteners, coloringagents, fluorescent agents, whitening agents, UV absorbers, lightstabilizers, defoaming agents, processing aids, antioxidants,stabilizers, softening agents, fragrance components, plasticizers,impact modifiers, titanium dioxide, acid copolymer wax, surfactants,rubber regrind (recycled core material), clay, mica, talc, glass flakes,milled glass, and mixtures thereof. Suitable additives are more fullydescribed in, for example, Rajagopalan et al., U.S. Patent ApplicationPublication No. 2003/0225197, the entire disclosure of which is herebyincorporated herein by reference. In a particular embodiment, the totalamount of additive(s) and filler(s) present in the final thermoplasticionomeric composition is 25 wt. % or less, or 20 wt. % or less, or 15wt. % or less, or 12 wt. % or less, or 10 wt. % or less, or 9 wt. % orless, or 6 wt. % or less, or 5 wt. % or less, or 4 wt. % or less, or 3wt. % or less, based on total weight of the ionomeric composition.

The acid copolymer ionomer is used in an amount of at least about 5% byweight based on total weight of composition and is generally present inan amount of about 5% to about 100%, or an amount within a range havinga lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upperlimit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, theconcentration of acid copolymer is about 40 to about 95 weight percent.

In a particular embodiment, the thermoplastic outer core layer is formedfrom an HNP composition, wherein the HNP composition is formed byblending an acid polymer, a non-acid polymer, a cation source, and afatty acid or metal salt thereof. For purposes of the present invention,maleic anhydride modified polymers are defined herein as a non-acidpolymer despite having anhydride groups that can ring-open to the acidform during processing of the polymer to form the HNP compositionsherein. The maleic anhydride groups are grafted onto a polymer, arepresent at relatively very low levels, and are not part of the polymerbackbone, as is the case with the acid polymers, which are exclusivelyE/X and E/X/Y copolymers of ethylene and an acid, particularlymethacrylic acid and acrylic acid.

In a particular aspect of this embodiment, the acid polymer is selectedfrom ethylene-acrylic acid and ethylene-methacrylic acid copolymers,optionally containing a softening monomer selected from n-butyl acrylateand iso-butyl acrylate. The acid polymer preferably has an acid contentwith a range having a lower limit of 2 or 10 or 15 or 16 mol % and anupper limit of 20 or 25 or 26 or 30 mol %. Examples of particularlysuitable commercially available acid polymers include, but are notlimited to, those given in Table 1A below.

TABLE 1A Melt Index Softening (2.16 kg, Acid Monomer 190° C., AcidPolymer (wt %) (wt %) g/10 min) Nucrel ® 9-1 methacrylic acid n-butylacrylate 25 (9.0) (23.5) Nucrel ® 599 methacrylic acid none 450 (10.0)Nucrel ® 960 methyacrylic acid none 60 (15.0) Nucrel ® 0407 methacrylicacid none 7.5 (4.0) Nucrel ® 0609 methacrylic acid none 9 (6.0) Nucrel ®1214 methacrylic acid none 13.5 (12.0) Nucrel ® 2906 methacrylic acidnone 60 (19.0) Nucrel ® 2940 methacrylic acid none 395 (19.0) Nucrel ®30707 acrylic acid none 7 (7.0) Nucrel ® 31001 acrylic acid none 1.3(9.5) Nucrel ® AE methacrylic acid isobutyl acrylate 11 (2.0) (6.0)Nucrel ® 2806 acrylic acid none 60 (18.0) Nucrel ® 0403 methacrylic acidnone 3 (4.0) Nucrel ® 925 methacrylic acid none 25 (15.0) Escor ® AT-310acrylic acid methyl acrylate 6 (6.5) (6.5) Escor ® AT-325 acrylic acidmethyl acrylate 20 (6.0) (20.0) Escor ® AT-320 acrylic acid methylacrylate 5 (6.0) (18.0) Escor ® 5070 acrylic acid none 30 (9.0) Escor ®5100 acrylic acid none 8.5 (11.0) Escor ® 5200 acrylic acid none 38(15.0) A-C ® 5120 acrylic acid none not (15) reported A-C ® 540 acrylicacid none not (5) reported A-C ® 580 acrylic acid none not (10) reportedPrimacor ® 3150 acrylic acid none 5.8 (6.5) Primacor ® 3330 acrylic acidnone 11 (3.0) Primacor ® 5985 acrylic acid none 240 (20.5) Primacor ®5986 acrylic acid none 300 (20.5) Primacor ® 5980I acrylic acid none 300(20.5) Primacor ® 5990I acrylic acid none 1300 (20.0) XUS 60751.17acrylic acid none 600 (19.8) XUS 60753.02L acrylic acid none 60 (17.0)Nucrel ® acid polymers are commercially available from E. I. du Pont deNemours and Company. Escor ® acid polymers are commercially availablefrom ExxonMobil Chemical Company. A-C ® acid polymers are commerciallyavailable from Honeywell International Inc. Primacor ® acid polymers andXUS acid polymers are commercially available from The Dow ChemicalCompany.

In another particular aspect of this embodiment, the non-acid polymer isan elastomeric polymer. Suitable elastomeric polymers include, but arenot limited to:

-   -   (a) ethylene-alkyl acrylate polymers, particularly        polyethylene-butyl acrylate, polyethylene-methyl acrylate, and        polyethylene-ethyl acrylate;    -   (b) metallocene-catalyzed polymers;    -   (c) ethylene-butyl acrylate-carbon monoxide polymers and        ethylene-vinyl acetate-carbon monoxide polymers;    -   (d) polyethylene-vinyl acetates;    -   (e) ethylene-alkyl acrylate polymers containing a cure site        monomer;    -   (f) ethylene-propylene rubbers and ethylene-propylene-diene        monomer rubbers;    -   (g) olefinic ethylene elastomers, particularly ethylene-octene        polymers, ethylene-butene polymers, ethylene-propylene polymers,        and ethylene-hexene polymers;    -   (h) styrenic block copolymers;    -   (i) polyester elastomers;    -   (j) polyamide elastomers;    -   (k) polyolefin rubbers, particularly polybutadiene,        polyisoprene, and styrene-butadiene rubber; and    -   (l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acidpolymers include, but are not limited to, Lotader® ethylene-alkylacrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, andparticularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900commercially available from Arkema Corporation; Elvaloy® ACethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC2116, AC3117, AC3427, and AC34035, commercially available from E. I. duPont de Nemours and Company; Fusabond® elastomeric polymers, such asethylene vinyl acetates, polyethylenes, metallocene-catalyzedpolyethylenes, ethylene propylene rubbers, and polypropylenes, andparticularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614,M603, E100, E158, E226, E265, E528, and E589, commercially availablefrom E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenesand ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C575, A-C 573, A-C 655, and A-C 395, commercially available fromHoneywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers,and Amplify® functional polymers, and particularly Amplify® GR 207, GR208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commerciallyavailable from The Dow Chemical Company; Enable® metallocenepolyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers,and Vistalon® EPDM rubber, commercially available from ExxonMobilChemical Company; Stafflex® metallocene linear low density polyethylene,commercially available from LyondellBasell; Elvaloy® HP4051, HP441,HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers andElvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxidepolymers, commercially available from E. I. du Pont de Nemours andCompany; Evatane® ethylene-vinyl acetate polymers having a vinyl acetatecontent of from 18 to 42%, commercially available from ArkemaCorporation; Elvax® ethylene-vinyl acetate polymers having a vinylacetate content of from 7.5 to 40%, commercially available from E. I. duPont de Nemours and Company; Vamac® G terpolymer of ethylene,methylacrylate and a cure site monomer, commercially available from E.I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commerciallyavailable from ExxonMobil Chemical Company; Kraton® styrenic blockcopolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT,commercially available from Kraton Performance Polymers Inc.; Septon®styrenic block copolymers, commercially available from Kuraray Co.,Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069,and 556, commercially available from E. I. du Pont de Nemours andCompany; Riteflex® polyester elastomers, commercially available fromCelanese Corporation; Pebax® thermoplastic polyether block amides, andparticularly Pebax® 2533, 3533, 4033, and 5533, commercially availablefrom Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify®ethylene-propylene copolymer elastomers, and Infuse® olefin blockcopolymers, commercially available from The Dow Chemical Company;Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially availablefrom ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularlyRoyaltuf® 498 maleic anhydride modified polyolefin based on an amorphousEPDM and Royaltuf® 485 maleic anhydride modified polyolefin based on ansemi-crystalline EPDM, commercially available from Chemtura Corporation.

Additional examples of particularly suitable commercially availableelastomeric polymers include, but are not limited to, those given inTable 1B below.

TABLE 1B Melt Index % Maleic (2.16 kg, 190° C., % Ester Anhydride g/10min) Polyethylene Butyl Acrylates Lotader ® 3210 6 3.1 5 Lotader ® 42106.5 3.6 9 Lotader ® 3410 17 3.1 5 Lotryl ® 17BA04 16-19 0 3.5-4.5Lotryl ® 35BA320 33-37 0 260-350 Elvaloy ® AC 3117 17 0 1.5 Elvaloy ® AC3427 27 0 4 Elvaloy ® AC 34035 35 0 40 Polyethylene Methyl AcrylatesLotader ® 4503 19 0.3 8 Lotader ® 4603 26 0.3 8 Lotader ® AX 8900 26 8%GMA 6 Lotryl ® 24MA02 23-26 0 1-3 Elvaloy ® AC 12024S 24 0 20 Elvaloy ®AC 1330 30 0 3 Elvaloy ® AC 1335 35 0 3 Elvaloy ® AC 1224 24 0 2Polyethylene Ethyl Acrylates Lotader ® 6200 6.5 2.8 40 Lotader ® 82006.5 2.8 200 Lotader ® LX 4110 5 3.0 5 Lotader ® HX 8290 17 2.8 70Lotader ® 5500 20 2.8 20 Lotader ® 4700 29 1.3 7 Lotader ® 4720 29 0.3 7Elvaloy ® AC 2116 16 0 1

The acid polymer and non-acid polymer are combined and reacted with acation source, such that at least 80% of all acid groups present areneutralized. The present invention is not meant to be limited by aparticular order for combining and reacting the acid polymer, non-acidpolymer and cation source. In a particular embodiment, the fatty acid ormetal salt thereof is used in an amount such that the fatty acid ormetal salt thereof is present in the HNP composition in an amount offrom 10 wt % to 60 wt %, or within a range having a lower limit of 10 or20 or 30 or 40 wt % and an upper limit of 40 or 50 or 60 wt %, based onthe total weight of the HNP composition. Suitable cation sources andfatty acids and metal salts thereof are further disclosed above.

In another particular aspect of this embodiment, the acid polymer is anethylene-acrylic acid polymer having an acid content of 19 wt % orgreater, the non-acid polymer is a metallocene-catalyzed ethylene-butenecopolymer, optionally modified with maleic anhydride, the cation sourceis magnesium, and the fatty acid or metal salt thereof is magnesiumoleate present in the composition in an amount of 20 to 50 wt %, basedon the total weight of the composition.

Other suitable thermoplastic polymers that may be used to form the outercore layer include, but are not limited to, the following polymers,including homopolymers, copolymers, and derivatives thereof:

(a) polyesters, particularly those modified with a compatibilizing groupsuch as sulfonate or phosphonate, including modified poly(ethyleneterephthalate), modified poly(butylene terephthalate), modifiedpoly(propylene terephthalate), modified poly(trimethyleneterephthalate), modified poly(ethylene naphthenate), and those disclosedin U.S. Pat. Nos. 6,353,050, 6,274,298, and 6,001,930, the entiredisclosures of which are hereby incorporated herein by reference, andblends of two or more thereof;

(b) polyamides, polyamide-ethers, and polyamide-esters, and thosedisclosed in U.S. Pat. Nos. 6,187,864, 6,001,930, and 5,981,654, theentire disclosures of which are hereby incorporated herein by reference,and blends of two or more thereof;

(c) polyurethanes, polyureas, polyurethane-polyurea hybrids, and blendsof two or more thereof;

(d) fluoropolymers, such as those disclosed in U.S. Pat. Nos. 5,691,066,6,747,110 and 7,009,002, the entire disclosures of which are herebyincorporated herein by reference, and blends of two or more thereof;

(e) polystyrenes, such as poly(styrene-co-maleic anhydride),acrylonitrile-butadiene-styrene, poly(styrene sulfonate), polyethylenestyrene, and blends of two or more thereof;

(f) polyvinyl chlorides and grafted polyvinyl chlorides, and blends oftwo or more thereof;

(g) polycarbonates, blends ofpolycarbonate/acrylonitrile-butadiene-styrene, blends ofpolycarbonate/polyurethane, blends of polycarbonate/polyester, andblends of two or more thereof;

(h) polyethers, such as polyarylene ethers, polyphenylene oxides, blockcopolymers of alkenyl aromatics with vinyl aromatics and polyamicesters,and blends of two or more thereof;

(i) polyimides, polyetherketones, polyamideimides, and blends of two ormore thereof; and

(j) polycarbonate/polyester copolymers and blends.

These thermoplastic polymers may be used by and in themselves to formthe outer core layer, or blends of thermoplastic polymers including theabove-described polymers and ethylene acid copolymer ionomers may beused. It also is recognized that the ionomer compositions may contain ablend of two or more ionomers. For example, the composition may containa 50/50 wt. % blend of two different highly-neutralizedethylene/methacrylic acid copolymers. In another version, thecomposition may contain a blend of one or more ionomers and a maleicanhydride-grafted non-ionomeric polymer. The non-ionomeric polymer maybe a metallocene-catalyzed polymer. In another version, the compositioncontains a blend of a highly-neutralized ethylene/methacrylic acidcopolymer and a maleic anhydride-grafted metallocene-catalyzedpolyethylene. In yet another version, the composition contains amaterial selected from the group consisting of highly-neutralizedionomers optionally blended with a maleic anhydride-graftednon-ionomeric polymer; polyester elastomers; polyamide elastomers; andcombinations of two or more thereof.

It also is recognized that thermoplastic materials can be “converted”into thermoset materials by cross-linking the polymer chains so theyform a network structure, and such cross-linked thermoplastic materialsmay be used to form the core layers in accordance with this invention.For example, thermoplastic polyolefins such as linear low densitypolyethylene (LLDPE), low density polyethylene (LDPE), and high densitypolyethylene (HDPE) may be cross-linked to form bonds between thepolymer chains. The cross-linked thermoplastic material typically hasimproved physical properties and strength over non-cross-linkedthermoplastics, particularly at temperatures above the crystallinemelting point. Preferably a partially or fully-neutralized ionomer, asdescribed above, is covalently cross-linked to render it into athermoset composition (that is, it contains at least some level ofcovalent, irreversable cross-links). Thermoplastic polyurethanes andpolyureas also may be converted into thermoset materials in accordancewith the present invention.

The cross-linked thermoplastic material may be created by exposing thethermoplastic to: 1) a high-energy radiation treatment, such as electronbeam or gamma radiation, such as disclosed in U.S. Pat. No. 5,891,973,which is incorporated by reference herein, 2) lower energy radiation,such as ultra-violet (UV) or infra-red (IR) radiation; 3) a solutiontreatment, such as an isocyanate or a silane; 4) incorporation ofadditional free radical initiator groups in the thermoplastic prior tomolding; and/or 5) chemical modification, such as esterification orsaponification, to name a few.

Modifications in thermoplastic polymeric structure of thermoplastic canbe induced by a number of methods, including exposing the thermoplasticmaterial to high-energy radiation or through a chemical process usingperoxide. Radiation sources include, but are not limited to, gamma-rays,electrons, neutrons, protons, x-rays, helium nuclei, or the like. Gammaradiation, typically using radioactive cobalt atoms and allows forconsiderable depth of treatment, if necessary. For core layers requiringlower depth of penetration, electron-beam accelerators or UV and IRlight sources can be used. Useful UV and IR irradiation methods aredisclosed in U.S. Pat. Nos. 6,855,070 and 7,198,576, which areincorporated herein by reference. The thermoplastic core layers may beirradiated at dosages greater than 0.05 Mrd, preferably ranging from 1Mrd to 20 Mrd, more preferably from 2 Mrd to 15 Mrd, and most preferablyfrom 4 Mrd to 10 Mrd. In one preferred embodiment, the cores areirradiated at a dosage from 5 Mrd to 8 Mrd and in another preferredembodiment, the cores are irradiated with a dosage from 0.05 Mrd to 3Mrd, more preferably 0.05 Mrd to 1.5 Mrd.

For example, a core assembly having a thermoplastic layer may beconverted to a thermoset layer by placing the core assembly on a slowlymove along a channel. Radiation from a radiation source, such as gammarays, is allowed to contact the surface of the cores. The source ispositioned to provide a generally uniform dose of radiation to the coresas they roll along the channel. The speed of the cores as they passthrough the radiation source is easily controlled to ensure the coresreceive sufficient dosage to create the desired hardness gradient. Thecores are irradiated with a dosage of 1 or more Mrd, more preferably 2Mrd to 15 Mrd. The intensity of the dosage is typically in the range of1 MeV to 20 MeV. For thermoplastic resins having a reactive group (e.g.,ionomers, thermoplastic urethanes, and the like), treating thethermoplastic core layer in a chemical solution of an isocyanate or anamine affects cross-linking and provides a harder surface and subsequenthardness gradient. Incorporation of peroxide or other free-radicalinitiator in the thermoplastic polymer, prior to molding or forming,also allows for heat curing on the molded core layer to create thedesired hardness gradient. By proper selection of time/temperature, anannealing process can be used to create a gradient. Suitable annealingand/or peroxide (free radical) methods are such as disclosed in U.S.Pat. Nos. 5,274,041 and 5,356,941, respectively, which are incorporatedby reference herein. Additionally, silane or amino-silane crosslinkingmay also be employed as disclosed in U.S. Pat. No. 7,279,529, thedisclosure of which incorporated herein by reference. The core layer maybe chemically treated in a solution, such as a solution containing oneor more isocyanates, to form the desired “positive hardness gradient.”The cores are typically exposed to the solution containing theisocyanate by immersing them in a bath at a particular temperature for agiven time. Exposure time should be greater than 1 minute, preferablyfrom 1 minute to 120 minutes, more preferably 5 minutes to 90 minutes,and most preferably 10 minutes to 60 minutes. In one preferredembodiment, the cores are immersed in the treating solution from 15minutes to 45 minutes, more preferably from 20 minutes to 40 minutes,and most preferably from 25 minutes to 30 minutes.

The core layers may be chemically treated in a solution, such as asolution containing one or more isocyanates, to form the desired“positive hardness gradient.” The cores are typically exposed to thesolution containing the isocyanate by immersing them in a bath at aparticular temperature for a given time. Exposure time should be greaterthan 1 minute, preferably from 1 minute to 120 minutes, more preferably5 minutes to 90 minutes, and most preferably 10 minutes to 60 minutes.In one preferred embodiment, the cores are immersed in the treatingsolution from 15 minutes to 45 minutes, more preferably from 20 minutesto 40 minutes, and most preferably from 25 minutes to 30 minutes. Bothirradiative and chemical methods promote molecular bonding, orcross-links, within the TP polymer. Radiative methods permitcross-linking and grafting in situ on finished products andcross-linking occurs at lower temperatures with radiation than withchemical processing. Chemical methods depend on the particular polymer,the presence of modifying agents, and variables in processing, such asthe level of irradiation. Significant property benefits in thethermoplastic materials can be attained and include, but are not limitedto, improved thermomechanical properties; lower permeability andimproved chemical resistance; reduced stress cracking; and overallimprovement in physical toughness.

Additional embodiments involve the use of plasticizers to treat the corelayers, thereby creating a softer outer portion of the core for a“negative” hardness gradient. The plasticizer may be reactive (such ashigher alkyl acrylates) or non-reactive (that is, phthalates,dioctylphthalate, or stearamides, etc). Other suitable plasticizersinclude, but are not limited to, oxa acids, fatty amines, fatty amides,fatty acid esters, phthalates, adipates, and sebacates. Oxa acids arepreferred plasticizers, more preferably those having at least one or twoacid functional groups and a variety of different chain lengths.Preferred oxa acids include 3,6-dioxaheptanoic acid,3,6,9-trioxadecanoic acid, diglycolic acid, 3,6,9-trioxaundecanoic acid,polyglycol diacid, and 3,6-dioxaoctanedioic acid, such as thosecommercially available from Archimica of Wilmington, Del. Any means ofchemical degradation will also result in a “negative” hardness gradient.Chemical modifications such as esterification or saponification are alsosuitable for modification of the thermoplastic core layer surface andcan result in the desired “positive hardness gradient.

Core Structure

As discussed above, the core of the golf ball of this inventionpreferably has a dual-layered structure comprising an inner core andouter core layer. Referring to FIG. 3, one version of a golf ball thatcan be made in accordance with this invention is generally indicated at(20). The ball (20) contains a dual-layered core (22) having an innercore (center) (22 a) and outer core layer (22 b) surrounded by asingle-layered cover (24). The inner core (22 a) is relatively small involume and generally has a diameter within a range of about 0.10 toabout 1.10 inches. More particularly, the inner core (22 a) preferablyhas a diameter size with a lower limit of about 0.15 or 0.25 or 0.35 or0.45 or 0.55 inches and an upper limit of about 0.60 or 0.70 or 0.80 or0.90 inches. In one preferred version, the diameter of the inner core(22 a) is in the range of about 0.025 to about 0.080 inches, morepreferably about 0.030 to about 0.075 inches. Meanwhile, the outer corelayer (22 b) generally has a thickness within a range of about 0.010 toabout 0.250 inches and preferably has a lower limit of 0.010 or 0.020 or0.025 or 0.030 inches and an upper limit of 0.070 or 0.080 or 0.100 or0.200 inches. In one preferred version, the outer core layer has athickness in the range of about 0.040 to about 0.170 inches, morepreferably about 0.060 to about 0.150 inches.

Referring to FIG. 4, in another version, the golf ball (25) contains adual-core (26) having an inner core (center) (26 a) and outer core layer(26 b). The dual-core (26) is surrounded by a multi-layered cover (28)having an inner cover layer (28 a) and outer cover layer (28 b).

The hardness of the core sub-assembly (inner core and outer core layer)is an important property. In general, cores with relatively highhardness values have higher compression and tend to have good durabilityand resiliency. However, some high compression balls are stiff and thismay have a detrimental effect on shot control and placement. Thus, theoptimum balance of hardness in the core sub-assembly needs to beattained.

In one preferred golf ball, the inner core (center) has a “positive”hardness gradient (that is, the outer surface of the inner core isharder than its geometric center); and the outer core layer has a“positive” hardness gradient (that is, the outer surface of the outercore layer is harder than the inner surface of the outer core layer.) Insuch cases where both the inner core and outer core layer each has a“positive” hardness gradient, the outer surface hardness of the outercore layer is preferably greater than the hardness of the geometriccenter of the inner core. In one preferred version, the positivehardness gradient of the inner core is in the range of about 2 to about40 Shore C units and even more preferably about 10 to about 25 Shore Cunits; while the positive hardness gradient of the outer core is in therange of about 2 to about 20 Shore C and even more preferably about 3 toabout 10 Shore C.

In an alternative version, the inner core may have a positive hardnessgradient; and the outer core layer may have a “zero” hardness gradient(that is, the hardness values of the outer surface of the outer corelayer and the inner surface of the outer core layer are substantiallythe same) or a “negative” hardness gradient (that is, the outer surfaceof the outer core layer is softer than the inner surface of the outercore layer.) For example, in one version, the inner core has a positivehardness gradient; and the outer core layer has a negative hardnessgradient in the range of about 2 to about 25 Shore C. In a secondalternative version, the inner core may have a zero or negative hardnessgradient; and the outer core layer may have a positive hardnessgradient. Still yet, in another embodiment, both the inner core andouter core layers have zero or negative hardness gradients.

In general, hardness gradients are further described in Bulpett et al.,U.S. Pat. Nos. 7,537,529 and 7,410,429, the disclosures of which arehereby incorporated by reference. Methods for measuring the hardness ofthe inner core and outer core layers along with other layers in the golfball and determining the hardness gradients of the various layers aredescribed in further detail below. The core layers have positive,negative, or zero hardness gradients defined by hardness measurementsmade at the outer surface of the inner core (or outer surface of theouter core layer) and radially inward towards the center of the innercore (or inner surface of the outer core layer). These measurements aremade typically at 2-mm increments as described in the test methodsbelow. In general, the hardness gradient is determined by subtractingthe hardness value at the innermost portion of the component beingmeasured (for example, the center of the inner core or inner surface ofthe outer core layer) from the hardness value at the outer surface ofthe component being measured (for example, the outer surface of theinner core or outer surface of the outer core layer).

Positive Hardness Gradient. For example, if the hardness value of theouter surface of the inner core is greater than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfaceharder than its geometric center), the hardness gradient will be deemed“positive” (a larger number minus a smaller number equals a positivenumber.) For example, if the outer surface of the inner core has ahardness of 67 Shore C and the geometric center of the inner core has ahardness of 60 Shore C, then the inner core has a positive hardnessgradient of 7. Likewise, if the outer surface of the outer core layerhas a greater hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a positivehardness gradient.

Negative Hardness Gradient. On the other hand, if the hardness value ofthe outer surface of the inner core is less than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfacesofter than its geometric center), the hardness gradient will be deemed“negative.” For example, if the outer surface of the inner core has ahardness of 68 Shore C and the geometric center of the inner core has ahardness of 70 Shore C, then the inner core has a negative hardnessgradient of 2. Likewise, if the outer surface of the outer core layerhas a lesser hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a negativehardness gradient.

Zero Hardness Gradient. In another example, if the hardness value of theouter surface of the inner core is substantially the same as thehardness value of the inner core's geometric center (that is, thesurface of the inner core has about the same hardness as the geometriccenter), the hardness gradient will be deemed “zero.” For example, ifthe outer surface of the inner core and the geometric center of theinner core each has a hardness of 65 Shore C, then the inner core has azero hardness gradient. Likewise, if the outer surface of the outer corelayer has a hardness value approximately the same as the inner surfaceof the outer core layer, the outer core layer will be considered to havea zero hardness gradient.

More particularly, the term, “positive hardness gradient” as used hereinmeans a hardness gradient of positive 3 Shore C or greater, preferably 7Shore C or greater, more preferably 10 Shore C, and even more preferably20 Shore C or greater. The term, “zero hardness gradient” as used hereinmeans a hardness gradient of less than 3 Shore C, preferably less than 1Shore C and may have a value of zero or negative 1 to negative 10 ShoreC. The term, “negative hardness gradient” as used herein means ahardness value of less than zero, for example, negative 3, negative 5,negative 7, negative 10, negative 15, or negative 20 or negative 25. Theterms, “zero hardness gradient” and “negative hardness gradient” may beused herein interchangeably to refer to hardness gradients of negative 1to negative 10.

The inner core preferably has a geometric center hardness(H_(inner core center)) of about 5 Shore D or greater. For example, the(H_(inner core center)) may be in the range of about 5 to about 88 ShoreD and more particularly within a range having a lower limit of about 5or 10 or 14 or 18 or 20 or 26 or 30 or 34 or 36 or 38 or 42 or 48 or 50or 52 Shore D and an upper limit of about 54 or 56 or 58 or 60 or 62 or64 or 68 or 70 or 74 or 76 or 80 or 82 or 84 or 88 Shore D. In anotherexample, the center hardness of the inner core (H_(inner core center)),as measured in Shore C units, is preferably about 10 Shore C or greater;for example, the H_(inner core center) may have a lower limit of about10 or 12 or 14 or 16 or 20 or 22 or 23 or 24 or 28 or 31 or 34 or 37 or40 or 44 or 52 or 58 Shore C and an upper limit of about 46 or 48 or 50or 51 or 53 or 55 or 58 or 61 or 62 or 65 or 68 or 71 or 74 or 76 or 78or 79 or 80 or 84 or 90 Shore C. Concerning the outer surface hardnessof the inner core (H_(inner core surface)), this hardness is preferablyabout 12 Shore D or greater or about 15 Shore D or greater; for example,the H_(inner core surface) may fall within a range having a lower limitof about 12 or 15 or 18 or 20 or 22 or 23 or 26 or 30 or 34 or 36 or 38or 42 or 48 or 50 or 52 Shore D and an upper limit of about 54 or 56 or58 or 60 or 62 or 70 or 72 or 75 or 78 or 80 or 82 or 84 or 86 or 90Shore D. In one version, the outer surface hardness of the inner core(H_(inner core surface)), as measured in Shore C units, has a lowerlimit of about 13 or 15 or 18 or 20 or 22 or 24 or 27 or 28 or 30 or 32or 34 or 38 or 44 or 47 or 48 or 58 or 60 or 70 or 74 Shore C and anupper limit of about 50 or 54 or 56 or 61 or 65 or 66 or 68 or 70 or 73or 76 or 78 or 80 or 84 or 86 or 88 or 90 or 92 Shore C. In anotherversion, the geometric center hardness (H_(inner core center)) is in therange of about 10 Shore C to about 50 Shore C; and the outer surfacehardness of the inner core (H_(inner core surface)) is in the range ofabout 5 Shore C to about 50 Shore C or in the range of about 5 Shore Cto about 48 Shore C.

On the other hand, the outer core layer preferably has an outer surfacehardness (H_(outer surface of OC)) of about 40 Shore D or greater, andmore preferably within a range having a lower limit of about 40 or 42 or44 or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90Shore D. The outer surface hardness of the outer core layer(H_(outer surface of OC)), as measured in Shore C units, preferably hasa lower limit of about 40 or 42 or 43 or 45 or 48 or 50 or 54 or 58 or60 or 63 or 65 or 67 or 70 or 72 or 73 or 76 Shore C, and an upper limitof about 78 or 80 or 84 or 85 or 87 or 88 or 89 or 90 or 92 or 95 ShoreC. And, the inner surface of the outer core layer(H_(inner surface of OC)) preferably has a hardness of about 40 Shore Dor greater, and more preferably within a range having a lower limit ofabout 40 or 42 or 44 or 46 or 48 or 50 or 52 and an upper limit of about54 or 56 or 58 or 60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or87 or 88 or 90 Shore D. The inner surface hardness of the outer corelayer (H_(inner surface of OC)), as measured in Shore C units,preferably has a lower limit of about 40 or 42 or 44 or 45 or 47 or 50or 52 or 54 or 55 or 58 or 60 or 63 or 65 or 67 or 70 or 73 or 76 ShoreC, and an upper limit of about 78 or 80 or 85 or 87 or 88 or 89 or 90 or92 or 95 Shore C.

In one embodiment, the outer surface hardness of the outer core layer(H_(outer surface of OC)), is less than the outer surface hardness(H_(inner core surface)) of the inner core by at least 3 Shore C unitsand more preferably by at least 5 Shore C.

In another embodiment, the outer surface hardness of the outer corelayer (H_(outer surface of OC)), is greater than the outer surfacehardness (H_(inner core surface)) of the inner core by at least 3 ShoreC units and more preferably by at least 5 Shore C.

The core structure also has a hardness gradient across the entire coreassembly. In one embodiment, the (H_(inner core center)) is in the rangeof about 10 Shore C to about 60 Shore C, preferably about 20 Shore C toabout 50 Shore C; and the (H_(outer surface of OC)) is in the range ofabout 40 Shore C to about 90 Shore C, preferably about 43 Shore C toabout 87 Shore C, to provide a positive hardness gradient across thecore assembly. In another embodiment, the (H_(inner core center)) is inthe range of about 10 Shore C to about 60 Shore C, preferably about 13Shore C to about 55 Shore C; and the (H_(outer surface of OC)) is in therange of about 65 to about 96 Shore C, preferably about 68 Shore C toabout 94 Shore C or about 75 Shore C to about 93 Shore C, to provide apositive hardness gradient across the core assembly. The gradient acrossthe core assembly will vary based on several factors including, but notlimited to, the dimensions of the inner core, intermediate core, andouter core layers.

As discussed above, the inner core is preferably formed from a foamedthermoplastic or thermoset composition and more preferably foamedpolyurethanes. And, the outer core layer is formed preferably from anon-foamed thermoset composition or a non-foamed thermoplasticcomposition.

The inner core preferably has a diameter in the range of about 0.100 toabout 1.100 inches. For example, the inner core may have a diameterwithin a range of about 0.100 to about 0.500 inches. In another example,the inner core may have a diameter within a range of about 0.300 toabout 0.800 inches. More particularly, the inner core may have adiameter size with a lower limit of about 0.10 or 0.12 or 0.15 or 0.25or 0.30 or 0.35 or 0.45 or 0.55 inches and an upper limit of about 0.60or 0.65 or 0.70 or 0.80 or 0.90 or 1.00 or 1.10 inches. As far as theouter core layer is concerned, it preferably has a thickness in therange of about 0.100 to about 0.750 inches. For example, the lower limitof thickness may be about 0.050 or 0.100 or 0.150 or 0.200 or 0.250 or0.300 or 0.340 or 0.400 and the upper limit may be about 0.500 or 0.550or 0.600 or 0.650 or 0.700 or 0.750 inches.

Dual-layered core structures containing layers with various thicknessand volume levels may be made in accordance with this invention. Forexample, in one version, the total diameter of the core structure is0.20 inches and the total volume of the core structure is 0.23 cc. Moreparticularly, in this example, the diameter of the inner core is 0.10inches and the volume of the inner core is 0.10 cc; while the thicknessof the outer core is 0.100 inches and the volume of the outer core is0.13 cc. In another version, the total core diameter is about 1.55inches and the total core volume is 31.96 cc. In this version, the outercore layer has a thickness of 0.400 inches and volume of 28.34 cc.Meanwhile, the inner core has a diameter of 0.75 inches and volume of3.62 cm. In one embodiment, the volume of the outer core layer isgreater than the volume of the inner core. In another embodiment, thevolume of the outer core layer and inner core are equivalent. In stillanother embodiment, the volume of the outer core layer is less than thevolume of the inner core. Other examples of core structures containinglayers of varying thicknesses and volumes are described below in Table1C.

TABLE 1C Sample Core Dimensions Foamed Volume Total Total Outer OuterInner of Core Core Core Core Core Inner Example Diameter VolumeThickness Volume Diameter Core A 0.30″  0.23 cc 0.100″  0.13 cc 0.10″ 0.10 cc B 1.60″ 33.15 cc 0.750″ 33.05 cc 0.10″  0.10 cc C 1.55″ 31.96cc 0.225″ 11.42 cc 1.10″ 11.42 cc D 1.55″ 31.96 cc 0.400″ 28.34 cc 0.75″ 3.62 cc E 1.55″ 31.96 cc 0.525″ 28.34 cc 0.50″  3.62 cc

In one preferred embodiment, the inner core has a specific gravity inthe range of about 0.25 to about 1.25 g/cc. Also, as discussed above,the specific gravity of the inner core may vary at different points ofthe inner core structure. That is, there may be a specific gravitygradient in the inner core. For example, in one preferred version, thegeometric center of the inner core has a density in the range of about0.25 to about 0.75 g/cc; while the outer skin of the inner core has adensity in the range of about 0.75 to about 1.50 g/cc.

Meanwhile, the outer core layer preferably has a relatively highspecific gravity. Thus, the specific gravity of the inner core layer(SG_(inner)) is preferably less than the specific gravity of the outercore layer (SG_(outer)). By the term, “specific gravity of the outercore layer” (“SG_(outer)”), it is generally meant the specific gravityof the outer core layer as measured at any point of the outer corelayer. The specific gravity values at different points in the outer corelayer may vary. That is, there may be specific gravity gradients in theouter core layer similar to the inner core. For example, the outer corelayer may have a specific gravity within a range having a lower limit ofabout 0.50 or 0.60 or 0.70 or 0.75 or 0.85 or 0.90 or 0.95 or 1.00 or1.10 or 1.25 or 1.30 or 1.36 or 1.40 or 1.42 or 1.48 or 1.50 or 1.60 or1.66 or 1.75 or 2.00 and an upper limit of 2.50 or 2.60 or 2.80 or 2.90or 3.00 or 3.10 or 3.25 or 3.50 or 3.60 or 3.80 or 4.00, 4.25 or 5.00 or5.10 or 5.20 or 5.30 or 5.40 or 6.00 or 6.20 or 6.25 or 6.30 or 6.40 or6.50 or 7.00 or 7.10 or 7.25 or 7.50 or 7.60 or 7.65 or 7.80 or 8.00 or8.20 or 8.50 or 9.00 or 9.75 or 10.00 g/cc.

In general, the specific gravities of the respective pieces of an objectaffect the Moment of Inertia (MOI) of the object. The Moment of Inertiaof a ball (or other object) about a given axis generally refers to howdifficult it is to change the ball's angular motion about that axis. Ifthe ball's mass is concentrated towards the center (the center piece(for example, inner core) has a higher specific gravity than the outerpiece (for example, outer core layers), less force is required to changeits rotational rate, and the ball has a relatively low Moment ofInertia. In such balls, most of the mass is located close to the ball'saxis of rotation and less force is needed to generate spin. Thus, theball has a generally high spin rate as the ball leaves the club's faceafter making impact. Conversely, if the ball's mass is concentratedtowards the outer surface (the outer piece (for example, outer corelayers) has a higher specific gravity than the center piece (forexample, inner core), more force is required to change its rotationalrate, and the ball has a relatively high Moment of Inertia. That is, insuch balls, most of the mass is located away from the ball's axis ofrotation and more force is needed to generate spin. Such balls have agenerally low spin rate as the ball leaves the club's face after makingimpact.

More particularly, as described in Sullivan, U.S. Pat. No. 6,494,795 andLadd et al., U.S. Pat. No. 7,651,415, the formula for the Moment ofInertia for a sphere through any diameter is given in the CRC StandardMathematical Tables, 24th Edition, 1976 at 20 (hereinafter CRCreference). The term, “specific gravity” as used herein, has itsordinary and customary meaning, that is, the ratio of the density of asubstance to the density of water at 4° C., and the density of water atthis temperature is 1 g/cm³.

In one embodiment, the golf balls of this invention are relatively lowspin and long distance. That is, the foam core construction, asdescribed above, wherein the inner core is made of a foamed compositionhelps provide a relatively low spin ball having good resiliency. Theinner foam cores of this invention preferably have a Coefficient ofRestitution (COR) of about 0.300 or greater; more preferably about 0.400or greater, and even more preferably about 0.450 or greater. Theresulting balls containing the dual-layered core constructions of thisinvention and cover of at least one layer preferably have a COR of about0.700 or greater, more preferably about 0.730 or greater; and even morepreferably about 0.750 to 0.810 or greater. The inner foam corespreferably have a Soft Center Deflection Index (“SCDI”) compression, asdescribed in the Test Methods below, in the range of about 50 to about190, and more preferably in the range of about 60 to about 170.

The USGA has established a maximum weight of 45.93 g (1.62 ounces) forgolf balls. For play outside of USGA rules, the golf balls can beheavier. In one preferred embodiment, the weight of the multi-layeredcore is in the range of about 28 to about 38 grams. Also, golf ballsmade in accordance with this invention can be of any size, although theUSGA requires that golf balls used in competition have a diameter of atleast 1.68 inches. For play outside of United States Golf Association(USGA) rules, the golf balls can be of a smaller size. Normally, golfballs are manufactured in accordance with USGA requirements and have adiameter in the range of about 1.68 to about 1.80 inches. As discussedfurther below, the golf ball contains a cover which may be multi-layeredand in addition may contain intermediate (casing) layers, and thethickness levels of these layers also must be considered. Thus, ingeneral, the dual-layer core structure normally has an overall diameterwithin a range having a lower limit of about 1.00 or 1.20 or 1.30 or1.40 inches and an upper limit of about 1.58 or 1.60 or 1.62 or 1.66inches, and more preferably in the range of about 1.3 to 1.65 inches. Inone embodiment, the diameter of the core sub-assembly is in the range ofabout 1.45 to about 1.62 inches.

Cover Structure

The golf ball sub-assemblies of this invention may be enclosed with oneor more cover layers. The golf ball sub-assembly may comprise themulti-layered core structure as discussed above. In other versions, thegolf ball sub-assembly includes the core structure and one or morecasing (mantle) layers disposed about the core. In one particularlypreferred version, the golf ball includes a multi-layered covercomprising inner and outer cover layers. The inner cover layer ispreferably formed from a composition comprising an ionomer or a blend oftwo or more ionomers that helps impart hardness to the ball. In aparticular embodiment, the inner cover layer is formed from acomposition comprising a high acid ionomer. A particularly suitable highacid ionomer is Surlyn 8150® (DuPont). Surlyn 8150® is a copolymer ofethylene and methacrylic acid, having an acid content of 19 wt %, whichis 45% neutralized with sodium. In another particular embodiment, theinner cover layer is formed from a composition comprising a high acidionomer and a maleic anhydride-grafted non-ionomeric polymer. Aparticularly suitable maleic anhydride-grafted polymer is Fusabond 525D®(DuPont). Fusabond 525D® is a maleic anhydride-grafted,metallocene-catalyzed ethylene-butene copolymer having about 0.9 wt %maleic anhydride grafted onto the copolymer. A particularly preferredblend of high acid ionomer and maleic anhydride-grafted polymer is an 84wt %/16 wt % blend of Surlyn 8150® and Fusabond 525D®. Blends of highacid ionomers with maleic anhydride-grafted polymers are furtherdisclosed, for example, in U.S. Pat. Nos. 6,992,135 and 6,677,401, theentire disclosures of which are hereby incorporated herein by reference.

The inner cover layer also may be formed from a composition comprising a50/45/5 blend of Surlyn® 8940/Surlyn® 9650/Nucrel® 960, and, in aparticularly preferred embodiment, the composition has a materialhardness of from 80 to 85 Shore C. In yet another version, the innercover layer is formed from a composition comprising a 50/25/25 blend ofSurlyn® 8940/Surlyn® 9650/Surlyn® 9910, preferably having a materialhardness of about 90 Shore C. The inner cover layer also may be formedfrom a composition comprising a 50/50 blend of Surlyn® 8940/Surlyn®9650, preferably having a material hardness of about 86 Shore C. Acomposition comprising a 50/50 blend of Surlyn® 8940 and Surlyn® 7940also may be used. Surlyn® 8940 is an E/MAA copolymer in which the MAAacid groups have been partially neutralized with sodium ions. Surlyn®9650 and Surlyn® 9910 are two different grades of E/MAA copolymer inwhich the MAA acid groups have been partially neutralized with zincions. Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt% methacrylic acid.

A wide variety of materials may be used for forming the outer coverincluding, for example, polyurethanes; polyureas; copolymers, blends andhybrids of polyurethane and polyurea; olefin-based copolymer ionomerresins (for example, Surlyn® ionomer resins and DuPont HPF® 1000 andHPF® 2000, commercially available from DuPont; Iotek® ionomers,commercially available from ExxonMobil Chemical Company; Amplify® IOionomers of ethylene acrylic acid copolymers, commercially availablefrom The Dow Chemical Company; and Clarix® ionomer resins, commerciallyavailable from A. Schulman Inc.); polyethylene, including, for example,low density polyethylene, linear low density polyethylene, and highdensity polyethylene; polypropylene; rubber-toughened olefin polymers;acid copolymers, for example, poly(meth)acrylic acid, which do notbecome part of an ionomeric copolymer; plastomers; flexomers;styrene/butadiene/styrene block copolymers;styrene/ethylene-butylene/styrene block copolymers; dynamicallyvulcanized elastomers; copolymers of ethylene and vinyl acetates;copolymers of ethylene and methyl acrylates; polyvinyl chloride resins;polyamides, poly(amide-ester) elastomers, and graft copolymers ofionomer and polyamide including, for example, Pebax® thermoplasticpolyether block amides, commercially available from Arkema Inc;cross-linked trans-polyisoprene and blends thereof; polyester-basedthermoplastic elastomers, such as Hytrel®, commercially available fromDuPont or RiteFlex®, commercially available from Ticona EngineeringPolymers; polyurethane-based thermoplastic elastomers, such asElastollan®, commercially available from BASF; synthetic or naturalvulcanized rubber; and combinations thereof. Castable polyurethanes,polyureas, and hybrids of polyurethanes-polyureas are particularlydesirable because these materials can be used to make a golf ball havinghigh resiliency and a soft feel. By the term, “hybrids of polyurethaneand polyurea,” it is meant to include copolymers and blends thereof.

Polyurethanes, polyureas, and blends, copolymers, and hybrids ofpolyurethane/polyurea are also particularly suitable for forming coverlayers. When used as cover layer materials, polyurethanes and polyureascan be thermoset or thermoplastic. Thermoset materials can be formedinto golf ball layers by conventional casting or reaction injectionmolding techniques. Thermoplastic materials can be formed into golf balllayers by conventional compression or injection molding techniques.

The compositions used to make the casing (mantle) and cover layers maycontain a wide variety of fillers and additives to impart specificproperties to the ball. For example, relatively heavy-weight andlight-weight metal fillers such as, particulate; powders; flakes; andfibers of copper, steel, brass, tungsten, titanium, aluminum, magnesium,molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth,bronze, silver, gold, and platinum, and alloys and combinations thereofmay be used to adjust the specific gravity of the ball. Other additivesand fillers include, but are not limited to, optical brighteners,coloring agents, fluorescent agents, whitening agents, UV absorbers,light stabilizers, surfactants, processing aids, antioxidants,stabilizers, softening agents, fragrance components, plasticizers,impact modifiers, titanium dioxide, clay, mica, talc, glass flakes,milled glass, and mixtures thereof.

The inner cover layer preferably has a material hardness within a rangehaving a lower limit of 70 or 75 or 80 or 82 Shore C and an upper limitof 85 or 86 or 90 or 92 Shore C. The thickness of the intermediate layeris preferably within a range having a lower limit of 0.010 or 0.015 or0.020 or 0.030 inches and an upper limit of 0.035 or 0.045 or 0.080 or0.120 inches. The outer cover layer preferably has a material hardnessof 85 Shore C or less. The thickness of the outer cover layer ispreferably within a range having a lower limit of 0.010 or 0.015 or0.025 inches and an upper limit of 0.035 or 0.040 or 0.055 or 0.080inches. Methods for measuring hardness of the layers in the golf ballare described in further detail below.

A single cover or, preferably, an inner cover layer is formed around theouter core layer. When an inner cover layer is present, an outer coverlayer is formed over the inner cover layer. Most preferably, the innercover is formed from an ionomeric material and the outer cover layer isformed from a polyurethane material, and the outer cover layer has ahardness that is less than that of the inner cover layer. Preferably,the inner cover has a hardness of greater than about 60 Shore D and theouter cover layer has a hardness of less than about 60 Shore D. In analternative embodiment, the inner cover layer is comprised of apartially or fully neutralized ionomer, a thermoplastic polyesterelastomer such as Hytrel™, commercially available form DuPont, athermoplastic polyether block amide, such as Pebax™, commerciallyavailable from Arkema, Inc., or a thermoplastic or thermosettingpolyurethane or polyurea, and the outer cover layer is comprised of anionomeric material. In this alternative embodiment, the inner coverlayer has a hardness of less than about 60 Shore D and the outer coverlayer has a hardness of greater than about 55 Shore D and the innercover layer hardness is less than the outer cover layer hardness.

As discussed above, the core structure of this invention may be enclosedwith one or more cover layers. In one embodiment, a multi-layered covercomprising inner and outer cover layers is formed, where the inner coverlayer has a thickness of about 0.01 inches to about 0.06 inches, morepreferably about 0.015 inches to about 0.040 inches, and most preferablyabout 0.02 inches to about 0.035 inches. In this version, the innercover layer is formed from a partially- or fully-neutralized ionomerhaving a Shore D hardness of greater than about 55, more preferablygreater than about 60, and most preferably greater than about 65. Theouter cover layer, in this embodiment, preferably has a thickness ofabout 0.015 inches to about 0.055 inches, more preferably about 0.02inches to about 0.04 inches, and most preferably about 0.025 inches toabout 0.035 inches, with a hardness of about Shore D 80 or less, morepreferably 70 or less, and most preferably about 60 or less. The innercover layer is harder than the outer cover layer in this version. Apreferred outer cover layer is a castable or reaction injection moldedpolyurethane, polyurea or copolymer, blend, or hybrid thereof having aShore D hardness of about 40 to about 50. In another multi-layer cover,dual-core embodiment, the outer cover and inner cover layer materialsand thickness are the same but, the hardness range is reversed, that is,the outer cover layer is harder than the inner cover layer. For thisharder outer cover/softer inner cover embodiment, the ionomer resinsdescribed above would preferably be used as outer cover material.

Manufacturing of Golf Balls

As described above, the inner core preferably is formed by a castingmethod. The outer core layer, which surrounds the inner core, is formedby molding compositions over the inner core. Compression or injectionmolding techniques may be used to form the other layers of the coresub-assembly. Then, the casing and/or cover layers are applied over thecore sub-assembly. Prior to this step, the core structure may besurface-treated to increase the adhesion between its outer surface andthe next layer that will be applied over the core. Suchsurface-treatment may include mechanically or chemically-abrading theouter surface of the core. For example, the core may be subjected tocorona-discharge, plasma-treatment, silane-dipping, or other treatmentmethods known to those in the art.

The cover layers are formed over the core or ball sub-assembly (the corestructure and any casing layers disposed about the core) using asuitable technique such as, for example, compression-molding,flip-molding, injection-molding, retractable pin injection-molding,reaction injection-molding (RIM), liquid injection-molding, casting,spraying, powder-coating, vacuum-forming, flow-coating, dipping,spin-coating, and the like. Preferably, each cover layer is separatelyformed over the ball subassembly. For example, an ethylene acidcopolymer ionomer composition may be injection-molded to producehalf-shells. Alternatively, the ionomer composition can be placed into acompression mold and molded under sufficient pressure, temperature, andtime to produce the hemispherical shells. The smooth-surfacedhemispherical shells are then placed around the core sub-assembly in acompression mold. Under sufficient heating and pressure, the shells fusetogether to form an inner cover layer that surrounds the sub-assembly.In another method, the ionomer composition is injection-molded directlyonto the core sub-assembly using retractable pin injection molding. Anouter cover layer comprising a polyurethane or polyurea composition overthe ball sub-assembly may be formed by using a casting process.

After the golf balls have been removed from the mold, they may besubjected to finishing steps such as flash-trimming, surface-treatment,marking, coating, and the like using techniques known in the art. Forexample, in traditional white-colored golf balls, the white-pigmentedcover may be surface-treated using a suitable method such as, forexample, corona, plasma, or ultraviolet (UV) light-treatment. Then,indicia such as trademarks, symbols, logos, letters, and the like may beprinted on the ball's cover using pad-printing, ink-jet printing,dye-sublimation, or other suitable printing methods. Clear surfacecoatings (for example, primer and top-coats), which may contain afluorescent whitening agent, are applied to the cover. The resultinggolf ball has a glossy and durable surface finish.

In another finishing process, the golf balls are painted with one ormore paint coatings. For example, white primer paint may be appliedfirst to the surface of the ball and then a white top-coat of paint maybe applied over the primer. Of course, the golf ball may be painted withother colors, for example, red, blue, orange, and yellow. As notedabove, markings such as trademarks and logos may be applied to thepainted cover of the golf ball. Finally, a clear surface coating may beapplied to the cover to provide a shiny appearance and protect any logosand other markings printed on the ball.

Different ball constructions can be made using the core construction ofthis invention as shown in FIGS. 1-5 and 6A-6D. Such golf ballconstructions include, for example, five-piece, and six-piececonstructions. It should be understood that the golf balls shown inFIGS. 1-5 and 6A-6D are for illustrative purposes only, and they are notmeant to be restrictive. Other golf ball constructions can be made inaccordance with this invention.

For example, other constructions include a core sub-assembly having afoam or non-foam inner core (center); and a foam or non-foam outer corelayer. Dual-core sub-assemblies (inner core and outer core layer),wherein the inner core and/or the outer core layer is foamed also may bemade. Furthermore, the inner cover layer, which surrounds the coresub-assembly, may be foamed or non-foamed. As discussed above,thermoplastic and thermoset foam compositions may be used to form thedifferent layers. Where more than one foam layer is used in a singlegolf ball, the foamed composition may be the same or different, and thecomposition may have the same or different hardness or specific gravityvalues. For example, a golf ball may contain a dual-core having a foamedcenter with a specific gravity of about 0.40 g/cc and a geometric centerhardness of about 50 Shore C and a center surface hardness of about 75Shore C that is formed from a polyurethane composition and an outer corelayer that is formed from a foamed highly neutralized ionomercomposition, wherein the outer core layer has a specific gravity ofabout 0.80 g/cc and a surface hardness of about 80 Shore C.

Test Methods

Hardness. The center hardness of a core is obtained according to thefollowing procedure. The core is gently pressed into a hemisphericalholder having an internal diameter approximately slightly smaller thanthe diameter of the core, such that the core is held in place in thehemispherical portion of the holder while concurrently leaving thegeometric central plane of the core exposed. The core is secured in theholder by friction, such that it will not move during the cutting andgrinding steps, but the friction is not so excessive that distortion ofthe natural shape of the core would result. The core is secured suchthat the parting line of the core is roughly parallel to the top of theholder. The diameter of the core is measured 90 degrees to thisorientation prior to securing. A measurement is also made from thebottom of the holder to the top of the core to provide a reference pointfor future calculations. A rough cut is made slightly above the exposedgeometric center of the core using a band saw or other appropriatecutting tool, making sure that the core does not move in the holderduring this step. The remainder of the core, still in the holder, issecured to the base plate of a surface grinding machine. The exposed‘rough’ surface is ground to a smooth, flat surface, revealing thegeometric center of the core, which can be verified by measuring theheight from the bottom of the holder to the exposed surface of the core,making sure that exactly half of the original height of the core, asmeasured above, has been removed to within 0.004 inches. Leaving thecore in the holder, the center of the core is found with a center squareand carefully marked and the hardness is measured at the center markaccording to ASTM D-2240. Additional hardness measurements at anydistance from the center of the core can then be made by drawing a lineradially outward from the center mark, and measuring the hardness at anygiven distance along the line, typically in 2 mm increments from thecenter. The hardness at a particular distance from the center should bemeasured along at least two, preferably four, radial arms located 180°apart, or 90° apart, respectively, and then averaged. All hardnessmeasurements performed on a plane passing through the geometric centerare performed while the core is still in the holder and without havingdisturbed its orientation, such that the test surface is constantlyparallel to the bottom of the holder, and thus also parallel to theproperly aligned foot of the durometer.

The outer surface hardness of a golf ball layer is measured on theactual outer surface of the layer and is obtained from the average of anumber of measurements taken from opposing hemispheres, taking care toavoid making measurements on the parting line of the core or on surfacedefects, such as holes or protrusions. Hardness measurements are madepursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic byMeans of a Durometer.” Because of the curved surface, care must be takento ensure that the golf ball or golf ball sub-assembly is centered underthe durometer indenter before a surface hardness reading is obtained. Acalibrated, digital durometer, capable of reading to 0.1 hardness unitsis used for the hardness measurements. The digital durometer must beattached to, and its foot made parallel to, the base of an automaticstand. The weight on the durometer and attack rate conforms to ASTMD-2240.

In certain embodiments, a point or plurality of points measured alongthe “positive” or “negative” gradients may be above or below a line fitthrough the gradient and its outermost and innermost hardness values. Inan alternative preferred embodiment, the hardest point along aparticular steep “positive” or “negative” gradient may be higher thanthe value at the innermost portion of the inner core (the geometriccenter) or outer core layer (the inner surface)—as long as the outermostpoint (i.e., the outer surface of the inner core) is greater than (for“positive”) or lower than (for “negative”) the innermost point (i.e.,the geometric center of the inner core or the inner surface of the outercore layer), such that the “positive” and “negative” gradients remainintact.

As discussed above, the direction of the hardness gradient of a golfball layer is defined by the difference in hardness measurements takenat the outer and inner surfaces of a particular layer. The centerhardness of an inner core and hardness of the outer surface of an innercore in a single-core ball or outer core layer are readily determinedaccording to the test procedures provided above. The outer surface ofthe inner core layer (or other optional intermediate core layers) in adual-core ball are also readily determined according to the proceduresgiven herein for measuring the outer surface hardness of a golf balllayer, if the measurement is made prior to surrounding the layer with anadditional core layer. Once an additional core layer surrounds a layerof interest, the hardness of the inner and outer surfaces of any inneror intermediate layers can be difficult to determine. Therefore, forpurposes of the present invention, when the hardness of the inner orouter surface of a core layer is needed after the inner layer has beensurrounded with another core layer, the test procedure described abovefor measuring a point located 1 mm from an interface is used.

Also, it should be understood that there is a fundamental differencebetween “material hardness” and “hardness as measured directly on a golfball.” For purposes of the present invention, material hardness ismeasured according to ASTM D2240 and generally involves measuring thehardness of a flat “slab” or “button” formed of the material. Surfacehardness as measured directly on a golf ball (or other sphericalsurface) typically results in a different hardness value. The differencein “surface hardness” and “material hardness” values is due to severalfactors including, but not limited to, ball construction (that is, coretype, number of cores and/or cover layers, and the like); ball (orsphere) diameter; and the material composition of adjacent layers. Italso should be understood that the two measurement techniques are notlinearly related and, therefore, one hardness value cannot easily becorrelated to the other. Shore hardness (for example, Shore C or Shore Dhardness) was measured according to the test method ASTM D-2240.

Compression. As disclosed in Jeff Dalton's Compression by Any OtherName, Science and Golf IV, Proceedings of the World Scientific Congressof Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), severaldifferent methods can be used to measure compression, including Atticompression, Riehle compression, load/deflection measurements at avariety of fixed loads and offsets, and effective modulus. For purposesof the present invention, compression refers to Soft Center DeflectionIndex (“SCDI”). The SCDI is a program change for the Dynamic CompressionMachine (“DCM”) that allows determination of the pounds required todeflect a core 10% of its diameter. The DCM is an apparatus that appliesa load to a core or ball and measures the number of inches the core orball is deflected at measured loads. A crude load/deflection curve isgenerated that is fit to the Atti compression scale that results in anumber being generated that represents an Atti compression. The DCM doesthis via a load cell attached to the bottom of a hydraulic cylinder thatis triggered pneumatically at a fixed rate (typically about 1.0 ft/s)towards a stationary core. Attached to the cylinder is an LVDT thatmeasures the distance the cylinder travels during the testing timeframe.A software-based logarithmic algorithm ensures that measurements are nottaken until at least five successive increases in load are detectedduring the initial phase of the test. The SCDI is a slight variation ofthis set up. The hardware is the same, but the software and output haschanged. With the SCDI, the interest is in the pounds of force requiredto deflect a core x amount of inches. That amount of deflection is 10%percent of the core diameter. The DCM is triggered, the cylinderdeflects the core by 10% of its diameter, and the DCM reports back thepounds of force required (as measured from the attached load cell) todeflect the core by that amount. The value displayed is a single numberin units of pounds.

Drop Rebound. By “drop rebound,” it is meant the number of inches asphere will rebound when dropped from a height of 72 inches in thiscase, measuring from the bottom of the sphere. A scale, in inches ismounted directly behind the path of the dropped sphere and the sphere isdropped onto a heavy, hard base such as a slab of marble or granite(typically about 1 ft wide by 1 ft high by 1 ft deep). The test iscarried out at about 72-75° F. and about 50% RH.

Coefficient of Restitution (“COR”). The COR is determined according to aknown procedure, wherein a golf ball or golf ball sub-assembly (forexample, a golf ball core) is fired from an air cannon at two givenvelocities and a velocity of 125 ft/s is used for the calculations.Ballistic light screens are located between the air cannon and steelplate at a fixed distance to measure ball velocity. As the ball travelstoward the steel plate, it activates each light screen and the ball'stime period at each light screen is measured. This provides an incomingtransit time period which is inversely proportional to the ball'sincoming velocity. The ball makes impact with the steel plate andrebounds so it passes again through the light screens. As the reboundingball activates each light screen, the ball's time period at each screenis measured. This provides an outgoing transit time period which isinversely proportional to the ball's outgoing velocity. The COR is thencalculated as the ratio of the ball's outgoing transit time period tothe ball's incoming transit time period(COR=V_(out)/V_(in)=T_(in)/T_(out)).

Density. The density refers to the weight per unit volume (typically,g/cm³) of the material and can be measured per ASTM D-1622.

The present invention is illustrated further by the following Examples,but these Examples should not be construed as limiting the scope of theinvention.

EXAMPLES

The examples below are for illustrative purposes only. In no manner isthe present invention limited to the specific disclosures therein.

In the following Examples, different foam formulations were used toprepare core samples using the above-described molding methods. Thedifferent formulations are described in Tables 2 and 3 below.

TABLE 2 (Sample A) Ingredient Weight Percent 4,4 Methylene DiphenylDiisocyanate (MDI) 14.65% Polyetratmethylene ether glycol (PTMEG 34.92%2000) *Mondur ™ 582 (2.5 fn) 29.11% Trifunctional caprolactone polyol(CAPA 20.22% 3031) (3.0 fn) Water 0.67% **Niax ™ L-1500 surfactant 0.04%*** KKAT ™ XK 614 catalyst 0.40% Dibutyl tin dilaurate (T-12) 0.03%*Mondur ™ 582 (2.5 fn) - polymeric methylene diphenyl diisocyanate(p-MDI) with 2.5 functionality, available from Bayer Material Science.**Niax ™ L-1500 silicone-based surfactant, available from MomentiveSpecialty Chemicals, Inc. *** KKAT ™ XK 614 zinc-based catalyst,available from King Industries.

The resulting spherical core Sample A (0.75 inch diameter) had a densityof 0.45 g/cm³, a compression (SCDI) of 75, and drop rebound of 46% basedon average measurements using the test methods as described above.

TABLE 3 (Sample B) Ingredient Weight Percent Mondur ™ 582 (2.5 fn)30.35% *Desmodur ™ 3900 aliphatic 30.35% **Polymeg ™ 650 19.43%***Ethacure ™ 300 19.43% Water 0.31% Niax ™ L-1500 surfactant 0.04%Dibutyl tin dilaurate (T-12) 0.09% *Desmodur ™ 3900 - polyfunctionalaliphatic polyisocyanate resin based on hexamethylene diisocyanate(HDI), available from Bayer Material Science. **Polymeg ™ 650 -polyetratmethylene ether glycol, available from Lyondell ChemicalCompany. ***Ethacure ™ 300 - aromatic diamine curing agent, availablefrom Albemarle Corp.

The resulting spherical core Sample B (0.75 inch diameter) had a densityof 0.61 g/cm³, a compression (SCDI) of 160, and drop rebound of 56%based on average measurements using the test methods as described above.

In the following Examples, different foam formulations were used toprepare single core samples using the above-described molding methods.The different formulations are described in Tables 4-8 below. Theresulting spherical cores were measured for density and tested forcompression and Coefficient of Restitution (COR) using the test methodsas described above and the results are reported in Tables 4-8.

Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term “parts per hundred,” also known as“phr,” is defined as the number of parts by weight of a particularcomponent present in a mixture, relative to 100 parts by weight of thebase rubber component. Mathematically, this can be expressed as theweight of an ingredient divided by the total weight of the polymer,multiplied by a factor of 100.

TABLE 4 Spherical Foam Core Samples Example No. 1 2 3 4 5 6 6.5% MDI 4143.72 45.01 33.58 49.48 31.83 Prepolymer Mondur MR 7.33 13.64 Mondur CD19.75 Mondur ML 17 13.06 8.06 Poly THF 650 22.2 13.06 29.01 CAPA 303113.77 13.77 4 CAPA 3091 27.86 CAPA 4101 CAPA 4801 D.I. Water 0.5 0.500.45 0.50 0.45 0.50 Niax 1500 0.75 0.75 0.75 0.75 0.75 Varox MPBCIrganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 Garamite 1958 0.375 0.3750.375 0.375 0.375 Total Parts 76.345 76.315 76.315 76.325 75.05 76.305Density 0.54 0.7 0.6 0.53 0.6 Compression 35 106 −217 −242 −217 CoR @125 ft/s 0.434 0.503 0.52 0.278 0.41 6.5% MDI Prepolymer is made from4,4′-MDI and polytetramethylene glycol ether Mondur ™ MR-polymeric MDI,available from Bayer. Mondur ™ CD-modified 4,4′-MDI, available fromBayer. Mondur ™ ML-isomer mixture of 2,4 and 4,4′-MDI, available fromBayer. Poly THF ™ 650-650 molecular weight polyetratmethylene etherglycol (PTMEG), available from BASF. CAPA ™ 3031-low molecular weighttrifunctional polycaprolactone polyol, available from Perstorp CAPA ™3091-polyester triol terminated by primary hydroxyl groups, availablefrom Perstorp. CAPA ™ 4101-tetra-functional polyol terminated withprimary hydroxyl groups, available from Perstorp. CAPA ™4801-tetra-functional polyol terminated with primary hydroxyl groups,available from Perstorp. Niax ™ L-1500-silicone surfactant fromMomentive Specialty Chemicals, Inc. Vanox ™ MBPC-antioxidant, availablefrom R.T. Vanderbuilt. Irganox ™ 1135-antioxidant, available BASF.Dabco ™ 33LV-tertiary amine catalyst, available from Air Products.Garamite ™ 1958-rheological additive, available from Southern Clay.

TABLE 5 Spherical Foam Core Samples Example No. 7 8 9 10 11 12 6.5% MDI21.67 45.81 49.22 45.01 45.01 55.8 Prepolymer Mondur MR 18.46 7.46 8.017.33 7.33 9.08 Mondur CD Mondur ML Poly THF 650 34.33 20.57 13 22.2 22.2CAPA 3031 0.7 4 9.66 CAPA 3091 CAPA 4101 CAPA 4801 D.I. Water 0.53 0.450.45 0.45 0.45 0.45 Niax 1500 0.75 0.75 0.75 0.75 0.75 0.75 Varox MPBC0.375 Irganox 1135 0.38 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 0.2 Garamite 19580.375 0.375 0.375 0.375 0.375 0.375 Total Parts 76.315 76.315 76.00576.69 76.695 76.315 Density 0.46 0.4 Compression −245 −109 CoR @ 125ft/s 0.388 0.515

TABLE 6 Spherical Foam Core Samples Example No. 13 14 15 16 17 18 6.5%MDI 68.81 44.28 33.1 42.39 49.48 40.75 Prepolymer Mondur MR 12.49 17.0511.96 8.06 11.5 Mondur CD Mondur ML Poly THF 650 CAPA 3031 5.79 5.0472.86 2.37 2 CAPA 3091 CAPA 4101 12.67 21.48 17.79 15 22.27 CAPA 4801D.I. Water 0.39 0.45 0.67 0.48 0.45 0.48 Niax 1500 0.75 0.75 0.75 0.750.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 0.2Garamite 1958 0.375 0.375 0.38 0.38 0.38 0.38 Total Parts 76.315 76.26276.49 76.32 76.32 76.33 Density 0.52 0.35 0.64 0.39 0.46 0.39Compression −200 −144 45 −135 −165 −120 CoR @ 125 ft/s 0.54 0.534 0.5710.553 0.537 0.543

TABLE 7 Spherical Foam Core Samples Example No. 19 20 21 22 6.5% MDIPrepolymer 47.83 56.05 29.18 19.58 Mondur MR 7.78 9.12 12.51 16.68Mondur CD Mondur ML Poly THF 650 CAPA 3031 CAPA 3091 CAPA 4101 18.9218.11 17.37 20.23 CAPA 4801 16.1 15.44 17.98 D.I. Water 0.45 0.61 0.50.52 Niax 1500 0.75 0.75 0.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV0.2 0.2 0.2 0.2 Garamite 1958 0.38 0.38 0.38 0.38 Total Parts 76.31101.32 76.33 76.32 Density 0.42 0.66 0.51 Compression −165 −169 −100 CoR@125 ft/s 0.609 0.492 0.425

TABLE 8 Spherical Foam Core Samples Example No. 23 24 25 26 6.5% MDIPrepolymer 43.87 50.63 37.21 43.57 Mondur MR 9.63 5.63 13.07 9.56 MondurCD Mondur ML Poly THF 650 CAPA 3031 CAPA 3091 CAPA 4101 18.36 15.9821.18 16.15 CAPA 4801 D.I. Water 0.47 0.45 0.49 0.47 Niax 1500 0.75 0.750.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 Garamite1958 0.38 0.38 0.38 0.38 Total Parts 76.31 76.33 76.34 76.33 Density0.46 0.57 0.43 0.48 Compression −164 −169 −137 −147 CoR @125 ft/s 0.5780.600 0.541 0.571

In the following Examples, different formulations were used to preparedual-core samples having a foam center and surrounding thermoset outercore layer using the above-described molding methods. The sample coreswere tested for compression (DCM), Coefficient of Restitution (COR), andhardness using the above-described test methods and the results arereported below in Table 13.

Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term “parts per hundred,” also known as“phr,” is defined as the number of parts by weight of a particularcomponent present in a mixture, relative to 100 parts by weight of thebase rubber component. Mathematically, this can be expressed as theweight of an ingredient divided by the total weight of the polymer,multiplied by a factor of 100.

Sample C (0.5″ Foamed Center)

In this Sample, the foam formulation in below Table 9 was used toprepare an inner core having a diameter of 0.5 inches.

TABLE 9 (Foam Center of Sample C) Ingredient Parts 6.5% MDI Prepolymer45.010 Mondur ™ 582 (2.5 fn) 7.330 Poly THF ™ 650 22.200 Deionized Water0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 19580.375

The following rubber formulation (Table 10) was molded about the foamedinner core and cured to form a thermoset rubber outer core layer.

TABLE 10 (Rubber Outer Core Layer of Sample C) Ingredient Parts *Buna ™CB23 100.0 Zinc Diacrylate (ZDA) 35.0 **Perkadox BC 0.5 ZincPentachlorothiophenol (ZnPCTP) 0.5 Zinc Oxide 14.9 *Buna ™ CB23 -polybutadiene rubber, available from Lanxess Corp. **Perkadox ™ BC,peroxide free-radical initiator, available from Akzo Nobel.

The dual-layered core of Sample C (foam center and thermoset rubberouter core layer with a center diameter of 0.5) inches was tested forhardness and the core was found to have a hardness gradient (across theentire core as measured at points in millimeters (mm) from the geometriccenter) in the range of about 21 Shore C to about 89 Shore C. Thehardness of the core measured at the geometric center was about 21 ShoreC and the hardness of the core measured at about 20 mm from thegeometric center (that is, the surface of the outer core layer) wasabout 89 Shore C. The hardness values measured at various points alongthis core structure are described in Table 17 below and the hardnessplot is shown in FIG. 5.

Sample D (0.5″ Foamed Center)

In this Sample D, the foam formulation in below Table 11 was used toprepare an inner core having a diameter of 0.5 inches.

TABLE 11 (Foam Center of Sample D) Ingredient Parts 6.5% MDI Prepolymer55.800 Mondur ™ 582 (2.5 fn) 9.080 CAPA ™ 3031 9.660 Deionized Water0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 19580.375

The same rubber formulation as described above in Sample C (Table 10)was molded about the foam center of Sample D and cured to form athermoset rubber outer core layer.

Sample E (0.5″ Foamed Center)

In this Sample E, the foam formulation in below Table 12 was used toprepare an inner core having a diameter of 0.5 inches.

TABLE 12 (Foam Center of Sample E) Ingredient Parts 6.5% MDI Prepolymer44.280 Mondur ™ 582 (2.5 fn) 12.490 CAPA ™ 3031 5.047 Deionized Water0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 19580.375

The same rubber formulation as described above in Sample C (Table 10)was molded about the foam center of Sample E and cured to form athermoset rubber outer core layer.

TABLE 13 Properties of Core Samples (C-E) Compression COR@125 SurfaceCenter Hardness Sample (DCM) ft/sec Hardness Hardness Gradient C 850.816 88.9 22.1 66.8 D 81 0.797 86.1 46.0 40.2 E 81 0.806 87.0 43.7 43.3

Sample F (0.75″ Foamed Center)

In this Sample, the foam formulation in below Table 14 was used toprepare an inner core having a diameter of 0.75 inches.

TABLE 14 (Foam Center of Sample F) Ingredient Parts 6.5% MDI Prepolymer47.830 Mondur ™ 582 (2.5 fn) 7.780 CAPA ™ 4101 18.920 Deionized Water0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 19580.380

In this Sample F, the following rubber formulation (Table 15) was moldedabout the foamed inner core and cured to form a thermoset rubber outercore layer. Different core samples having different densities (F1-F5)were prepared and are further described in Table 17 below.

TABLE 15 (Rubber Outer Core Layer of Sample F) Ingredient Parts Buna ™CB23 100.0 Zinc Diacrylate (ZDA) 36.0 Perkadox BC 0.5 ZincPentachlorothiophenol (ZnPCTP) 0.5 Zinc Oxide 21.3

The Sample F1-F5 cores were tested for compression (DCM), Coefficient ofRestitution (COR), and hardness using the above-described test methodsand the results are reported below in Table 16.

TABLE 16 Properties of Core Samples (F1-F5) Density of Foamed Compres-COR @ Surface Center Hardness Center sion 125 Hardness Hardness GradientSample (g/cm³) (DCM) ft/sec (Shore C) (Shore C) (Shore C) F-1 0.40 800.779 86.6 33.5 53.0 F-2 0.46 78 0.775 86.4 31.8 54.3 F-3 0.59 77 0.77086.4 34. 52.3 F-4 0.75 78 0.769 87.3 43.0 44.3 F-5 0.83 75 0.766 87.437.4 50.0

The dual-layered core of Sample F-2 (foam center and thermoset rubberouter core layer having a center diameter of 0.75 inches) was tested forhardness and the core was found to have a hardness gradient (across theentire core as measured at points in millimeters (mm) from the geometriccenter) in the range of about 32 Shore C to about 86 Shore C. Thehardness of the core measured at the geometric center was about 32 ShoreC and the hardness of the core measured at about 20 mm from thegeometric center (that is, the surface of the outer core layer) wasabout 86 Shore C. The hardness values measured at various points alongthe core structure are described in Table 17 below and the hardness plotis shown in FIG. 5.

TABLE 17 Hardness Properties of Core Samples (C and F-2) Distance fromHardness Hardness Geometric Center Gradient of Gradient of of CoreSample (mm) Sample C (Shore C) Sample F-2 (Shore C)  0 (Center) 21 31.82 20.8 32.6 4 25 35.7 6 28.1 35.1 8 72 37.8 10 72.8 70.9 12 73.1 70.2 1472.7 70.2 16 76.5 76.9 18 82.6 81.8 20 (Surface) 88.9 86.4

Set forth below are particularly suitable highly neutralized polymercompositions for forming thermoplastic core layers. The followingcommercially available materials were used in the below examples:

-   -   A-C® 5120 ethylene acrylic acid copolymer with an acrylic acid        content of 15%,    -   A-C® 5180 ethylene acrylic acid copolymer with an acrylic acid        content of 20%,    -   A-C® 395 high density oxidized polyethylene homopolymer, and    -   A-C® 575 ethylene maleic anhydride copolymer, commercially        available from Honeywell;    -   CB23 high-cis neodymium-catalyzed polybutadiene rubber,        commercially available from Lanxess Corporation;    -   CA1700 Soya fatty acid, CA1726 linoleic acid, and CA1725        conjugated linoleic acid, commercially available from Chemical        Associates;    -   Century® 1107 highly purified isostearic acid mixture of        branched and straight-chain C18 fatty acid, commercially        available from Arizona Chemical;    -   Clarix® 011370-01 ethylene acrylic acid copolymer with an        acrylic acid content of 13% and    -   Clarix® 011536-01 ethylene acrylic acid copolymer with an        acrylic acid content of 15%, commercially available from A.        Schulman Inc.;    -   Elvaloy® AC 1224 ethylene-methyl acrylate copolymer with a        methyl acrylate content of 24 wt %,    -   Elvaloy® AC 1335 ethylene-methyl acrylate copolymer with a        methyl acrylate content of 35 wt %,    -   Elvaloy® AC 2116 ethylene-ethyl acrylate copolymer with an ethyl        acrylate content of 16 wt %,    -   Elvaloy® AC 3427 ethylene-butyl acrylate copolymer having a        butyl acrylate content of 27 wt %, and    -   Elvaloy® AC 34035 ethylene-butyl acrylate copolymer having a        butyl acrylate content of 35 wt %, commercially available        from E. I. du Pont de Nemours and Company;    -   Escor® AT-320 ethylene acid terpolymer, commercially available        from ExxonMobil Chemical Company;    -   Exxelor® VA 1803 amorphous ethylene copolymer functionalized        with maleic anhydride, commercially available from ExxonMobil        Chemical Company;    -   Fusabond® N525 metallocene-catalyzed polyethylene,    -   Fusabond® N416 chemically modified ethylene elastomer,    -   Fusabond® C190 anhydride modified ethylene vinyl acetate        copolymer, and    -   Fusabond® P614 functionalized polypropylene, commercially        available from E. I. du Pont de Nemours and Company;    -   Hytrel® 3078 very low modulus thermoplastic polyester elastomer,        commercially available from E. I. du Pont de Nemours and        Company;    -   Kraton® FG 1901 GT linear triblock copolymer based on styrene        and ethylene/butylene with a polystyrene content of 30% and    -   Kraton® FG1924GT linear triblock copolymer based on styrene and        ethylene/butylene with a polystyrene content of 13%,        commercially available from Kraton Performance Polymers Inc.;    -   Lotader® 4603, 4700 and 4720, random copolymers of ethylene,        acrylic ester and maleic anhydride, commercially available from        Arkema Corporation;    -   Nordel® IP 4770 high molecular weight semi-crystalline EPDM        rubber, commercially available from The Dow Chemical Company;    -   Nucrel® 9-1, Nucrel® 599, Nucrel® 960, Nucrel® 0407, Nucrel®        0609, Nucrel® 1214, Nucrel® 2906, Nucrel® 2940, Nucrel® 30707,        Nucrel® 31001, and Nucrel® AE acid copolymers, commercially        available from E. I. du Pont de Nemours and Company;    -   Primacor® 3150, 3330, 5980I, and 5990I acid copolymers,        commercially available from The Dow Chemical Company;    -   Royaltuf® 498 maleic anhydride modified polyolefin based on an        amorphous EPDM, commercially available from Chemtura        Corporation;    -   Sylfat® FA2 tall oil fatty acid, commercially available from        Arizona Chemical;    -   Vamac® G terpolymer of ethylene, methylacrylate and a cure site        monomer, commercially available from E. I. du Pont de Nemours        and Company; and    -   XUS 60758.08L ethylene acrylic acid copolymer with an acrylic        acid content of 13.5%, commercially available from The Dow        Chemical Company.

Various compositions were melt blended using components as given inTable 18 below. The compositions were neutralized by adding a cationsource in an amount sufficient to neutralize, theoretically, 110% of theacid groups present in components 1 and 3, except for example 72, inwhich the cation source was added in an amount sufficient to neutralize75% of the acid groups. Magnesium hydroxide was used as the cationsource, except for example 68, in which magnesium hydroxide and sodiumhydroxide were used in an equivalent ratio of 4:1. In addition tocomponents 1-3 and the cation source, example 71 contains ethyl oleateplasticizer.

The relative amounts of component 1 and component 2 used are indicatedin Table 18 below, and are reported in wt %, based on the combinedweight of components 1 and 2. The relative amounts of component 3 usedare indicated in Table 18 below, and are reported in wt %, based on thetotal weight of the composition.

TABLE 18 Example Component 1 wt % Component 2 wt % Component 3 wt % 1Primacor 5980I 78 Lotader 4603 22 magnesium oleate 41.6 2 Primacor 5980I84 Elvaloy AC 1335 16 magnesium oleate 41.6 3 Primacor 5980I 78 ElvaloyAC 3427 22 magnesium oleate 41.6 4 Primacor 5980I 78 Elvaloy AC 1335 22magnesium oleate 41.6 5 Primacor 5980I 78 Elvaloy AC 1224 22 magnesiumoleate 41.6 6 Primacor 5980I 78 Lotader 4720 22 magnesium oleate 41.6 7Primacor 5980I 85 Vamac G 15 magnesium oleate 41.6 8 Primacor 5980I 90Vamac G 10 magnesium oleate 41.6 8.1 Primacor 5990I 90 Fusabond 614 10magnesium oleate 41.6 9 Primacor 5980I 78 Vamac G 22 magnesium oleate41.6 10 Primacor 5980I 75 Lotader 4720 25 magnesium oleate 41.6 11Primacor 5980I 55 Elvaloy AC 3427 45 magnesium oleate 41.6 12 Primacor5980I 55 Elvaloy AC 1335 45 magnesium oleate 41.6 12.1 Primacor 5980I 55Elvaloy AC 34035 45 magnesium oleate 41.6 13 Primacor 5980I 55 ElvaloyAC 2116 45 magnesium oleate 41.6 14 Primacor 5980I 78 Elvaloy AC 3403522 magnesium oleate 41.6 14.1 Primacor 5990I 80 Elvaloy AC 34035 20magnesium oleate 41.6 15 Primacor 5980I 34 Elvaloy AC 34035 66 magnesiumoleate 41.6 16 Primacor 5980I 58 Vamac G 42 magnesium oleate 41.6 17Primacor 5990I 80 Fusabond 416 20 magnesium oleate 41.6 18 Primacor5980I 100 — — magnesium oleate 41.6 19 Primacor 5980I 78 Fusabond 416 22magnesium oleate 41.6 20 Primacor 5990I 100 — — magnesium oleate 41.6 21Primacor 5990I 20 Fusabond 416 80 magnesium oleate 41.6 21.1 Primacor5990I 20 Fusabond 416 80 magnesium oleate 31.2 21.2 Primacor 5990I 20Fusabond 416 80 magnesium oleate 20.8 22 Clarix 011370 30.7 Fusabond 41669.3 magnesium oleate 41.6 23 Primacor 5990I 20 Royaltuf 498 80magnesium oleate 41.6 24 Primacor 5990I 80 Royaltuf 498 20 magnesiumoleate 41.6 25 Primacor 5990I 80 Kraton FG1924GT 20 magnesium oleate41.6 26 Primacor 5990I 20 Kraton FG1924GT 80 magnesium oleate 41.6 27Nucrel 30707 57 Fusabond 416 43 magnesium oleate 41.6 28 Primacor 5990I80 Hytrel 3078 20 magnesium oleate 41.6 29 Primacor 5990I 20 Hytrel 307880 magnesium oleate 41.6 30 Primacor 5980I 26.8 Elvaloy AC 34035 73.2magnesium oleate 41.6 31 Primacor 5980I 26.8 Lotader 4603 73.2 magnesiumoleate 41.6 32 Primacor 5980I 26.8 Elvaloy AC 2116 73.2 magnesium oleate41.6 33 Escor AT-320 30 Elvaloy AC 34035 52 magnesium oleate 41.6Primacor 5980I 18 34 Nucrel 30707 78.5 Elvaloy AC 34035 21.5 magnesiumoleate 41.6 35 Nucrel 30707 78.5 Fusabond 416 21.5 magnesium oleate 41.636 Primacor 5980I 26.8 Fusabond 416 73.2 magnesium oleate 41.6 37Primacor 5980I 19.5 Fusabond N525 80.5 magnesium oleate 41.6 38 Clarix011536-01 26.5 Fusabond N525 73.5 magnesium oleate 41.6 39 Clarix011370-01 31 Fusabond N525 69 magnesium oleate 41.6 39.1 XUS 60758.08L29.5 Fusabond N525 70.5 magnesium oleate 41.6 40 Nucrel 31001 42.5Fusabond N525 57.5 magnesium oleate 41.6 41 Nucrel 30707 57.5 FusabondN525 42.5 magnesium oleate 41.6 42 Escor AT-320 66.5 Fusabond N525 33.5magnesium oleate 41.6 43 Nucrel 2906/2940 21 Fusabond N525 79 magnesiumoleate 41.6 44 Nucrel 960 26.5 Fusabond N525 73.5 magnesium oleate 41.645 Nucrel 1214 33 Fusabond N525 67 magnesium oleate 41.6 46 Nucrel 59940 Fusabond N525 60 magnesium oleate 41.6 47 Nucrel 9-1 44.5 FusabondN525 55.5 magnesium oleate 41.6 48 Nucrel 0609 67 Fusabond N525 33magnesium oleate 41.6 49 Nucrel 0407 100 — — magnesium oleate 41.6 50Primacor 5980I 90 Fusabond N525 10 magnesium oleate 41.6 51 Primacor5980I 80 Fusabond N525 20 magnesium oleate 41.6 52 Primacor 5980I 70Fusabond N525 30 magnesium oleate 41.6 53 Primacor 5980I 60 FusabondN525 40 magnesium oleate 41.6 54 Primacor 5980I 50 Fusabond N525 50magnesium oleate 41.6 55 Primacor 5980I 40 Fusabond N525 60 magnesiumoleate 41.6 56 Primacor 5980I 30 Fusabond N525 70 magnesium oleate 41.657 Primacor 5980I 20 Fusabond N525 80 magnesium oleate 41.6 58 Primacor5980I 10 Fusabond N525 90 magnesium oleate 41.6 59 — — Fusabond N525 100magnesium oleate 41.6 60 Nucrel 0609 40 Fusabond N525 20 magnesiumoleate 41.6 Nucrel 0407 40 61 Nucrel AE 100 — — magnesium oleate 41.6 62Primacor 5980I 30 Fusabond N525 70 CA1700 soya fatty acid 41.6 magnesiumsalt 63 Primacor 5980I 30 Fusabond N525 70 CA1726 linoleic acid 41.6magnesium salt 64 Primacor 5980I 30 Fusabond N525 70 CA1725 conjugated41.6 linoleic acid magnesium salt 65 Primacor 5980I 30 Fusabond N525 70Century 1107 41.6 isostearic acid magnesium salt 66 A-C 5120 73.3Lotader 4700 26.7 oleic acid 41.6 magnesium salt 67 A-C 5120 73.3Elvaloy 34035 26.7 oleic acid 41.6 magnesium salt 68 Primacor 5980I 78.3Lotader 4700 21.7 oleic acid 41.6 magnesium salt and sodium salt 69Primacor 5980I 47 Elvaloy AC34035 13 — — A-C 5180 40 70 Primacor 5980I30 Fusabond N525 70 Sylfat FA2 41.6 magnesium salt 71 Primacor 5980I 30Fusabond N525 70 oleic acid 31.2 magnesium salt ethyl oleate 10 72Primacor 5980I 80 Fusabond N525 20 sebacic acid 41.6 magnesium salt 73Primacor 5980I 60 — — — — A-C 5180 40 74 Primacor 5980I 78.3 — — oleicacid 41.6 A-C 575 21.7 magnesium salt 75 Primacor 5980I 78.3 Exxelor VA1803 21.7 oleic acid 41.6 magnesium salt 76 Primacor 5980I 78.3 A-C 39521.7 oleic acid 41.6 magnesium salt 77 Primacor 5980I 78.3 Fusabond C19021.7 oleic acid 41.6 magnesium salt 78 Primacor 5980I 30 Kraton FG 190170 oleic acid 41.6 magnesium salt 79 Primacor 5980I 30 Royaltuf 498 70oleic acid 41.6 magnesium salt 80 A-C 5120 40 Fusabond N525 60 oleicacid 41.6 magnesium salt 81 Primacor 5980I 30 Fusabond N525 70 erucicacid 41.6 magnesium salt 82 Primacor 5980I 30 CB23 70 oleic acid 41.6magnesium salt 83 Primacor 5980I 30 Nordel IP 4770 70 oleic acid 41.6magnesium salt 84 Primacor 5980I 48 Fusabond N525 20 oleic acid 41.6 A-C5180 32 magnesium salt 85 Nucrel 2806 22.2 Fusabond N525 77.8 oleic acid41.6 magnesium salt 86 Primacor 3330 61.5 Fusabond N525 38.5 oleic acid41.6 magnesium salt 87 Primacor 3330 45.5 Fusabond N525 20 oleic acid41.6 Primacor 3150 34.5 magnesium salt 88 Primacor 3330 28.5 — — oleicacid 41.6 Primacor 3150 71.5 magnesium salt 89 Primacor 3150 67 FusabondN525 33 oleic acid 41.6 magnesium salt 90 Primacor 5980I 55 Elvaloy AC34035 45 oleic acid 31.2 magnesium salt ethyl oleate 10

Solid spheres of each composition were injection molded, and the solidsphere COR, compression, Shore D hardness, and Shore C hardness of theresulting spheres were measured after two weeks. The results arereported in Table 19 below. The surface hardness of a sphere is obtainedfrom the average of a number of measurements taken from opposinghemispheres, taking care to avoid making measurements on the partingline of the sphere or on surface defects, such as holes or protrusions.Hardness measurements are made pursuant to ASTM D-2240 “IndentationHardness of Rubber and Plastic by Means of a Durometer.” Because of thecurved surface, care must be taken to insure that the sphere is centeredunder the durometer indentor before a surface hardness reading isobtained. A calibrated, digital durometer, capable of reading to 0.1hardness units is used for all hardness measurements and is set torecord the maximum hardness reading obtained for each measurement. Thedigital durometer must be attached to, and its foot made parallel to,the base of an automatic stand. The weight on the durometer and attackrate conform to ASTM D-2240.

TABLE 19 Solid Sphere Solid Sphere Solid Sphere Solid Sphere Ex. CORCompression Shore D Shore C 1 0.845 120 59.6 89.2 2 * * * * 3 0.871 11757.7 88.6 4 0.867 122 63.7 90.6 5 0.866 119 62.8 89.9 6 * * * *7 * * * * 8 * * * * 8.1 0.869 127 65.3 92.9 9 * * * * 10 * * * *11 * * * * 12 0.856 101 55.7 82.4 12.1 0.857 105 53.2 81.3 13 * * * * 140.873 122 64.0 91.1 14.1 * * * * 15 * * * * 16 * * * * 17 0.878 117 60.189.4 18 0.853 135 67.6 94.9 19 * * * * 20 0.857 131 66.2 94.4 21 0.752 26 34.8 57.1 21.1 0.729  9 34.3 56.3 21.2 0.720  2 33.8 55.2 22 * * * *23 * * * * 24 * * * * 25 * * * * 26 * * * * 27 * * * * 28 * * * *29 * * * * 30 **  66 42.7 65.5 31 0.730  67 45.6 68.8 32 ** 100 52.478.2 33 0.760  64 43.6 64.5 34 0.814  91 52.8 80.4 35 * * * * 36 * * * *37 * * * * 38 * * * * 39 * * * * 39.1 * * * * 40 * * * * 41 * * * *42 * * * * 43 * * * * 44 * * * * 45 * * * * 46 * * * * 47 * * * *48 * * * * 49 * * * * 50 * * * * 51 0.873 121 61.5 90.2 52 0.870 11660.4 88.2 53 0.865 107 57.7 84.4 54 0.853  97 53.9 80.2 55 0.837  8250.1 75.5 56 0.818  66 45.6 70.7 57 0.787  45 41.3 64.7 58 0.768  2635.9 57.3 59 * * * * 60 * * * * 61 * * * * 62 * * * * 63 * * * *64 * * * * 65 * * * * 66 * * * * 67 * * * * 68 * * * * 69 * * * *70 * * * * 71 * * * * 72 * * * * 73 * * * * 74 * * * * 75 * * * *76 * * * * 77 * * * * 78 * * * * 79 * * * * 80 * * * * 81 * * * *82 * * * * 83 * * * * 84 * * * * 85 * * * * 86 * * * * 87 * * * *88 * * * * 89 * * * * 90 * * * * * not measured ** sphere broke duringmeasurement

Prophetic Examples

The following prophetic examples describe two-layered core structuresthat may be made in accordance with this invention. The foam center ofthe core may be made using a polyurethane foam formulation as describedabove in Tables 2 and 3 or any other suitable foam material as describeabove. The outer core layer may be made of an ethylene acid copolymerionomer or any other suitable thermoplastic material as described above.

Example 1

Two-layered core (foam center and thermoplastic outer layer) having acenter diameter of 0.5 inches and a hardness gradient across the core(as measured at points in millimeters (mm) from the geometric center) inthe range of about 41 Shore C to about 81 Shore C. The hardness plot ofthis core structure is shown in FIG. 6A.

Example 2

Two-layered core (foam center and thermoplastic outer layer) having acenter diameter of 0.5 inches and a hardness gradient across the core(as measured at mm points from the geometric center) in the range ofabout 26 Shore C to about 74 Shore C. The hardness plot of this corestructure is shown in FIG. 6B.

Example 3

Two-layered core (foam center and thermoplastic outer layer) having acenter diameter of 0.5 inches and a hardness gradient across the core(as measured at mm points from the geometric center) in the range ofabout 51 Shore C to about 73 Shore C. The hardness plot of this corestructure is shown in FIG. 6C.

Example 4

Two-layered core (foam center and thermoplastic outer layer) having acenter diameter of 0.75 inches and a hardness gradient across the core(as measured at mm points from the geometric center) in the range ofabout 24 Shore C to about 82 Shore C. The hardness plot of this corestructure is shown in FIG. 6D.

When numerical lower limits and numerical upper limits are set forthherein, it is contemplated that any combination of these values may beused.

All patents, publications, test procedures, and other references citedherein, including priority documents, are fully incorporated byreference to the extent such disclosure is not inconsistent with thisinvention and for all jurisdictions in which such incorporation ispermitted.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by those ofordinary skill in the art without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the examples and descriptions setforth herein, but rather that the claims be construed as encompassingall of the features of patentable novelty which reside in the presentinvention, including all features which would be treated as equivalentsthereof by those of ordinary skill in the art to which the inventionpertains.

What is claimed is:
 1. A core assembly for a golf ball, comprising: aninner core layer formed from a foamed composition, the inner core layerhaving a diameter of from 0.100 inches to 1.100 inches and an outersurface hardness (H_(inner core surface)) and a center hardness(H_(inner core center)), the H_(inner core surface) being greater thanthe H_(inner core center) to provide a positive hardness gradient; andan outer core layer formed from a non-foamed composition, the outer corelayer having a thickness of from 0.100 inches to 0.750 inches and anouter surface hardness (H_(outer surface of OC)) and an inner surfacehardness (H_(inner surface of OC)), the H_(outer surface of OC) beingthe same or less than the H_(inner surface of OC) to provide a zero ornegative hardness gradient; wherein the specific gravity of the outercore layer is greater than the specific gravity of the inner core layer;and wherein at least one of the inner core layer composition and theouter core layer composition is a highly neutralized polymer compositioncomprising: an acid copolymer of ethylene and an α,β-unsaturatedcarboxylic acid, optionally including a softening monomer selected fromthe group consisting of alkyl acrylates and methacrylates; a non-acidpolymer selected from the group consisting of polyolefins, polyamides,polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers,single-site catalyst polymerized polymers, ethylene propylene rubber,ethylene propylene diene rubber, styrenic block copolymer rubbers, alkylacrylate rubbers, and functionalized derivatives thereof; an organicacid or salt thereof; and a cation source present in an amountsufficient to neutralize greater than 80% of all acid groups present inthe composition.
 2. The core assembly of claim 1, wherein the acidcopolymer of ethylene and an α,β-unsaturated carboxylic acid does notinclude a softening monomer, the non-acid polymer is an alkyl acrylaterubber selected from ethylene-alkyl acrylates and ethylene-alkylmethacrylates, and the organic acid salt is magnesium oleate present inan amount of 20 parts or greater per 100 parts of acid copolymer andnon-acid copolymer combined.
 3. The core assembly of claim 1, whereinthe cation source is present in an amount sufficient to neutralize 110%or greater of all acid groups present in the composition.
 4. The coreassembly of claim 1, wherein the outer core layer composition isthermoplastic.
 5. The core assembly of claim 1, wherein the outer corelayer composition is thermoset, and wherein the inner core layercomposition is the highly neutralized polymer composition.
 6. A coreassembly for a golf ball, comprising: an inner core layer formed from afoamed composition, the inner core layer having a diameter of from 0.100inches to 1.100 inches and an outer surface hardness(H_(inner core surface)) and a center hardness (H_(inner core center)),the H_(inner core surface) being the same or less than theH_(inner core center) to provide a zero or negative hardness gradient;and an outer core layer formed from a non-foamed composition, the outercore layer having a thickness of from 0.100 inches to 0.750 inches andan outer surface hardness (H_(outer surface of OC)) and an inner surfacehardness (H_(inner surface of OC)), the H_(outer surface of OC) beingthe same or less than the H_(inner surface of OC) to provide a zero ornegative hardness gradient; wherein the specific gravity of the outercore layer is greater than the specific gravity of the inner core layer;and wherein at least one of the inner core layer composition and theouter core layer composition is a highly neutralized polymer compositioncomprising: an acid copolymer of ethylene and an α,β-unsaturatedcarboxylic acid, optionally including a softening monomer selected fromthe group consisting of alkyl acrylates and methacrylates; a non-acidpolymer selected from the group consisting of polyolefins, polyamides,polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers,single-site catalyst polymerized polymers, ethylene propylene rubber,ethylene propylene diene rubber, styrenic block copolymer rubbers, alkylacrylate rubbers, and functionalized derivatives thereof; an organicacid or salt thereof; and a cation source present in an amountsufficient to neutralize greater than 80% of all acid groups present inthe composition.
 7. The core assembly of claim 6, wherein the acidcopolymer of ethylene and an α,β-unsaturated carboxylic acid does notinclude a softening monomer, the non-acid polymer is an alkyl acrylaterubber selected from ethylene-alkyl acrylates and ethylene-alkylmethacrylates, and the organic acid salt is magnesium oleate present inan amount of 20 parts or greater per 100 parts of acid copolymer andnon-acid copolymer combined.
 8. The core assembly of claim 6, whereinthe cation source is present in an amount sufficient to neutralize 110%or greater of all acid groups present in the composition.
 9. The coreassembly of claim 6, wherein the outer core layer composition isthermoplastic.
 10. The core assembly of claim 6, wherein the outer corelayer composition is thermoset, and wherein the inner core layercomposition is the highly neutralized polymer composition.